Wishes as written won't work as a Power. Too exploitable.
Unlimited evothaum is worth about 2 Refresh.
Toughness should not be allowed to affect spellcasting costs.
For Wishes, I suggest using Aspect invocations or spellcasting with the Limitation custom Power.
Okay, I guess 3 Refresh for 4 extra spells isn't so terrible.
Making something expensive doesn't solve exploitability, really. The issue here is that the right way to use your proposed wish power is kind of dumb.
That right way, incidentally, is to get a compliant mortal to order you to do whatever you want.
That obviously isn't the intent, but there's really no point writing all that rules text if you're going to adjudicate informally anyway.
This is a really cool concept for a djinn. I hope you don't mind if I steal it.
From the djinn's standpoint, and narratively, that is what it would want. The idea is that it would trick mortals into allowing it to essentially run free. This is a trope based in many different pieces of fiction. You may think it's dumb from a game standpoint, but certainly not from a narrative one.
No, it's dumb from a narrative standpoint. Once a djinni gets one compliant mortal, he no longer cares much about wishes because he's at full power forever.
Except for the enchanted item thing, which has its own problems. A unlimited number of items really isn't a good idea.
1: No, his power is limited. He doesn't get the lore bonus.
2: He still has to have the mortal's permission for every spell and gives up his freedom/free will. If the mortal asks him to do something he doesn't want to do, he still has to at tha point. Basically, he'd be a slave (like they were to Solomon). Even a slave who can trick his master doesn't want the master.
This is a semi-long post. Skip to the end for a quick summary if you want.
A couple comments; not so much criticisms -
1. Extra spells per scene are already accomplished through mental consequences and mimicked by using enchanted items. I feel extra boxes for spells only could be a bad idea.
1a) Here's why: Players will want the ability to do that. Players should not be able to have such a power.
And even if being a slave is mandatory for multiple wishes from one source, that just makes Djinn with slave High Concepts broken.
That's the whole point of the Limitation rewrite, isn't it? Accomodating per-character/per-game costing?