Question

I've noticed that sometimes the prices for the items in my Join Avenue go down by 10-100 Pokedollars or so. When and how often does this happen?

Answer 1

In addition to that, as you increase the rank of the shop, the areas will give discounts of 1% for every rank up you get. This goes up to a 40% discount. You'll also receive a 50% discount for a week when you make all eight stores reach Rank 10.

Source