Cash them in for discount coupons for Pokemarts. 1 coin equals 1% discount on all purchases permanently. With a maximum of 50.
No. That's terrible.
But realistic. Do you think you'll just get handed rare items and abilities, or rare Pokemon for a few measly coins that everyone is capable of having hundreds of? It's not the best idea sure but it's realistic enough.
An immediate 50% discount is realistic? --- Currently awaiting: Lunar Knights 2, AC:NL, Pikmin 3, XY, WW HD, LR:FFXIII, X, LoZ U, FFVXIII Skarmory would slap the hell outta you