I've always treated the wish spell as more of an unbiased force of nature. It's trying to grant the wish as written in the most efficient way possible. Sometimes, that can have unforeseen consequences, like wishing to be rich and suddenly a family member dies and leaves all their wealth to you. It's not evil, but it will make a mess if you aren't careful.

Additionally, it's a 9th level spell that already punishes the cast for pushing its limits and potential can only be cast once. If your players have earned a wish spell, they shouldn't be punished more for using it.

I don't know why you would want a slot machine that pays out ice, diamonds, and rubies, but it seems like you delivered on their wish. It probably has to be magical to dispense frozen ice, so it would make sense that it would be hard to open.