You're assuming that a 1/day command word item of Wish is something that exists at all, and that it costs what you say it does. There's a reason that the magic item rules are in the DMG, not the PHB: Custom magic items don't exist unless the DM says that they do, and even if they do exist, there are no rules for their cost, only guidelines, because it's the DM making the decision.

At this point, you might as well just say "Ask your DM for unlimited wishes".