Wish Spell - how much gold can you wish for?

There's nothing much in the guidelines about wishing for objects. Would you allow it, or is it just "free money" if you can?

In money value, at a minimum it might be the cost of a scroll of a spell that Wish can duplicate. Would you add the casting cost of Wish? What's the maximum, if you allow it?

That's a good question. I really don't know but since its a 10th level spell maybe look at the Party Currency given per level on page 509 of the CRB. So if you wished for gold at 16th level, Use the Party Currency if they intend to share it with the party which would be 20,000 gp if not then use the Currency per Additional PC which would be 5,000 gp for a single Wish. At least it would make for a good guide line :)

Now how I've seen it done in past games at my table was normally when someone wishes for something that exists it takes it from somewhere else.

A friend of mine once wished for a lot of gold (100,000 gold) He ended up with an odd number like 78,245 gold which consisted of mostly coin but there were gold teeth, candle sticks, rings, jewelry.... His party was just outside of a near by town. The party Wizard got a bad feeling and so they split the gold between them and since they all had bags of holding it was very easy to carry.

They went into town and discovered that the wish took everyone's gold from not only from the nearby town but also from several towns from a 100 mile radius.

Needless to say the Wizard earned his gold that day. Since copper, silver and platinum were still around in this area they paid for everything in silver and platinum and took a ship bound for another city some 200 miles away and never went back :)

They had to deal with the fallout of that wish over the course of the next few campaigns. It was quite fun and annoying at the same time :)

Let's note that because the money component of the wish was removed in 2e it's power was reduced.

For it so stay balanced I would consider the "earn income" activity as a baseline. An alchemist feat (philosopher stone) already does something similar.
Here though it's not taking your day but just casting a spell. I would probably go for 50GP* without any drawback (possibly higher with bad effects like the previous post showed).

It's important to take into acount that any day a wizard doesn't use a wish slot they may use it for money at the end of the day.

*50GP is a bit less than what an expert level 19 character would earn. I did not make it too good because it's a 3 action spell meaning it doesn't even require your whole day like the philosopher stone.