It depends on how the Wish was used
The 5e spell Wish has two principle uses:
- Duplicate the effect of a spell of 8th level or lower, or
- Create some other (possibly stronger) effect, and suffer "Magical Backlash" as a consequence.
If you asked the Wizard to use their 9th level spell slot to reproduce the effects of a spell like Greater Restoration, then basically, you got an effect from him for free, without him (or anyone else) needing to provide the 100gp diamond material component; you might owe him an equivalent amount of gp for the convenience, since 100gp is [probably] more convenient to acquire than a physical 100gp diamond, plus perhaps a fee for using his one and only 9th level spell slot for the day, which he might have otherwise been able to put to another use.
Alternatively, he used it to reproduce spells like Lesser Restoration, Dispel Magic, Remove Curse, Mind Blank, or Heal, none of which have any Material components at all, consumed, costly, or otherwise. So you might owe him a small pittance for his time (in addition to the aforementioned opportunity cost of using a 9th level spell slot).
However. It might be possible that instead, the Wizard used the Wish to reproduce an effect that cannot be described by an 8th level (or lower) spell, if the effect placed on you was especially difficult to remove or dispel. In that case, the Wizard suffered 2d4 days of backlash (average 5 days) and suffered a 33% chance of never being able to cast Wish again. That's a tremendous burden and risk the Wizard assumed for the purposes of curing your ailment.
At this point, it becomes contingent on what your DM decides, but what your DM will take into consideration is how generous this Wizard is (are they a Good Samaritan who felt you deserved the help you received and paid no heed to the consequences against themself?) and how much they're willing to suffer the potential consequences of never being able to cast Wish ever again. Under most circumstances though, your debt to the wizard, in this case, would be quite extraordinary.