Something goofy is going on here. The price stays the same ($35.28) whether I select, small, medium or large. Also, Zazzle tells me the product hasn’t been viewed for more than 7 months, when Google Analytic tells me it has been viewed a couple of times at least.
the discounted prices are wrong on my end, too.
for my fleece blankets, only the large size shows 50% off the regular price correctly.
the small and medium size show incorrect promo prices.
for the link you’ve provided, only the medium size shows 50% off the regular price correctly.
the small and large size blankets show incorrect promo prices.
Yes, I noticed that also.
Hi all,
I’m sorry to hear that you encountered an error here. Thanks for sharing with us. I sent this to our team to investigate further.
Pádraig 
I just noticed this is also true all puzzles, for example:
Let’s use this conversation moving forward: https://community.zazzle.com/t5/technical-issues/the-sales-price-isn-t-updating-properly/m-p/47289
Engineering is aware of the issue. We’ll post updates in the other discussion.