I'm going to use The Fault in Our Stars as an example, but it's not the only one.
For Week 1, Best Buy had the Theatrical Version for $19.99. For Week 2, Best Buy lowered the price to $17.99.
For Week 1, Target had the Extended Version for $22.99. For Week 2, Target lowered the price to $19.99.
Furthermore, Fox added a $5 coupon on coupons.com on either the Sunday or Monday of Week 2.
https://forum.blu-ray.com/showthread.php?t=248860
I know why retailers do this. They sell many copies of movies during Week 1 and are gambling on people not asking for Price Adjustments.
However, specifically with TFIOS, the difference is as much as $8 depending on which version you buy. This results in making two trips: one trip during Week 1 to get the version that you want (exclusives or perhaps a mint slipcover) and then another trip during Week 2 to get a refund.
(Plus, it's probably safer to keep the movie new/sealed just in case Customer Service decides to be finicky.)