Correct non-monotonous pricing scheme
See http://www.shapeways.com/forum/index.php?t=rview&goto=40719
I flagged the problem of the non-monotonous pricing scheme already in April 2011.It is December now, and still the problem is not solved.
Oskar
shared this idea
Hi Everyone,
Recently Nancy emailed everyone on this list about the solution options and following the discussion and your feedback, we are leaving the pricing as is for right now.
We are working on a fairer solution for ALL pricing which consists of a bounding box + material volume + start up cost. This should get rid of the problem once and for all. We think that’s a better solution to work towards than doing a quick fix with the current density discount.
For all these reasons, I am closing this issue to return your votes to you.
Best,
Natalia
15 comments
-
nancyliang
commented
Hey guys, you should have received an e-mail from me about this issue containing some lovely Excel graphs showing the different options. Please let me know through e-mail your thoughts and if anything is unclear.
Thanks,
Nancy -
Adminbartv
(Admin, Shapeways)
commented
Hi all,
just to let you know that I'm now responsible for chasing this up with our product and development teams. Feel free to contact me at bart@shapeways.com if you want to.
In the mean time, I'm looking for some additional insight into the issue. Please have a read:
http://www.shapeways.com/forum/index.php?t=msg&goto=48731&#msg_48731
Thanks!
Bart
-
Oskar_van_Deventer
commented
Hi Pete,
> since it's now on the top of the list we will fix it shortly.
Three months have again passed, and over a year since we flagged this problem.Are you taking us seriously?
Oskar
-
pete
commented
Hi guys,
the proposal to charge
p(v)=1.5+1.4*v for d<0,1 and v<20cm3 and
p(v)=15.5+0.7*v for d>0.1 anv v>20cm3 makes sense and was the intended idea.Since there was no negative price-impact due to our wrong implementation, we did not give the fix top prio. Since it's now on the top of the list we will fix it shortly.
Pete
-
mctrivia commented
ana i understand not wanting to be haphazard. the formula i proposed gives a discount that we can already reach by adding garbage material to the print.
however it is nicer to you:
-you don't need to print the garbage material saving you material cost
-you don't know what material is garbage or not so you need to find and ship it which waists timenicer for us:
-we don't need to manually add the necisary extra material.We are not asking for anything to complicated just to adjust the formula system to compensate for what is already possible to do manually.
-
Adminbartv
(Admin, Shapeways)
commented
Hey guys, just wanted to get back to you on this issue. Originally this was implemented as a way to incentivize denser models (to take advantage of the build space), but we understand how it can also be troublesome for you in certain scenarios. There's a lot of factors to weigh here, which is why even though we knew it was a high priority ever since it hit Uservoice, we weren't able to throw down an immediate fix.
Because this issue greatly affects everybody, we don't want to act haphazardly. Sorry for the delay, and thanks for your patience while we work through this issue. [Ana]
-
yes technically not a bug in the sense that anything is broken. however it does cause unwanted results and is easy to fix.
ways to fix:
us) add junk material if d>5.4% and volume>20cc until d=10% you will get the discount and shapeways has to pay for extra time and money
shapeways) implement formula I provided. gives same price to us as above but saves shapeways money on printing junk material and improves customer satisfaction as there are no extra left over pieces. -
Giles Williams commented
If it is not a bug, then it is (at the very least) an undesirable feature. However, it is not a bug in code, or in a webpage, but in the pricing scheme which may not be the responsibility of technical staffer, but rather whoever decides the pricing schemes.
It should be noted that those complaining about the scheme are actually trying to point out ways to help save SW some money (even if it is by pointing out the expense of adding 'money saving cubes' to their designs.)
-
woops I made a math error. put 20 on wrong side of subtraction
p=min(xy,20*y+(x/(d/10)-20)*y/2)+c;
This pricing will result in newp for v=100cc. Please note that people can already get newp just by adding enough waist material to reach 10% density. oldp is the current pricing on the web site. as you can see the savings by adding material gets pretty high the closer you are to d=10%
-
sorry but your math is off.
you are correct in this though simkplifying is a bad idea as it makes price adjustments hard:
p=1.5+1.4*20*+0.7*(v-20)
p=1.5+28+0.7*v-0.7*20
p=1.5+28+0.7*v-14
p=15.5+0.7*vhowever the discount only applys to volume over 20cc so there will never be a situation where v<20 resulting in a lower price then the discout formula with a v of 20. assuming density is over 10% current forumlas give
v=19 p=28.1
v=20 p=29.5
v=21 p=30.2the formula I gave of
p=min(xy,20*y+(20-x/(d/10))*y/2)+c;
when v>20, and d<10 will give you the best price you could manually make it by adding enough volume to the model to get discount or leaving as is depending how formula lands. It fixes the jump in the middle of d<10 and d>10 and sets the price at a number that can already be reached by users by simply adding mass
bart. unless there was a post removed everyone has been keeping this cival.
-
Adminbartv
(Admin, Shapeways)
commented
Hi Tom,
yes I agree this should not happen. Reading Pete's comments this is not the way we intend the discount to work, that's why I've asked our devs to look in to it.
-
Tom van der Zanden commented
The price for WSF is specified as 1.5+1.4*v. The density discount applies to models where v>20 and d>0.1, in this case, the price is 15.5+0.7*v (this really is right, you are charged full price for the first 20 cm3 and then half price for the remaining cm3’s; so we would have 1.5+1.4*20*+0.7*(v-20) = 1.5+(1.4-0.7)*20+0.7*v=15.5*0.7*v.
However, there is a small oddity in the pricing; a model of 19 cm3 could become much cheaper by increasing the material to 20 cm3 and getting the discount, or a model that is not quite 10% dense could become much cheaper by adding a little volume to make it 10% dense.
It does not seem right that we have to change our model by adding extra volume to it to get the best possible price. It seems Shapeways could help us a little here and calculate the price as if we did add on the extra material.
If we are given bounding box volume b and model volume v, we could calculate v2 as MAX(v, 20, b/10) (this is the minimal volume that qualifies for the discount) and then the price should be calculated as MIN(1.5+1.4*v, 15.5+0.7*v2).
For WSF coloured you would use MIN(1.75+1.75*v, 19.25+0.875*v2) and WSFP would use MIN(1.5+1.75*v, 19+0.875*v2).
-
Adminbartv
(Admin, Shapeways)
commented
Please keep things neutral, I've updated the issue title.
Also, I'll forward this to development. [bart]
-
just in case not obvious. last code is only when x>20 otherwise it is always p=xy+c
-
solution.
p=price
x=volume
y=price/cc
c=startup
d=density(10=10%)if (d>10) {
p=20*y+(20-x)*y/2+c;
} else {
p=min(xy,20*y+(20-x/(d/10))*y/2)+c;
}this fixes by making a middle range where d<10 but if the volume was increased to 10% would result in cheaper print. it then calculate discount rate based on 10% density volume instead of actual density.
shapeways gets paid as if we added the extra mass to get the discount without us having to manually add or shapeways having to print
