Scion dealerships can change the prices as often as they want as long as the menus in the showroom & the website are updated for each one.
If you come across a dealer that is trying to gouge you by adding "Market Value Adjustment" labels, find another dealer (This coming from a salesman for 10 years at a Toyota/Scion dealer). It may be a further drive for some, but does that greedy dealer deserve your money to start with?
My store has a Hyundai franchise as well and our Hyundai competitors love to add $1,490 to the price for nothing. People appreciate transparency and like that we work off of MSRP instead an inflated amount and are willing to drive past the other dealers to get to us. The one positive thing about these bump labels are that it makes my job easier.
Ruskymx