I've pull back website from penalization

OK,the website was penalized big time from google console and needed 2.5 months to get in regular state even better to start nice rankings.
The owners wanted to get it back because website is old and bonded with their names.
I charge it as my regular SEO fee.
It is in attorney niche,basically is for USA law offices.Previous guys Indian I think fucked up big time with PBN links.
Now big question to you is that when I reinstate and rankings started to climb in first 7 spots on google page 1 for local area search how much to ask from owners to be paid.
They are please with my work and demand to reward me.
What you think guys to ask some sum of amount or to insist on making long term deal with them-Contract on 12 or 24 months.
I have dilemma here so any advise will be helpful.

seo in uk is 1k a month on contract .

getting back a valuable website is miricle on it own 5k would be fair.

remember if you didnt get it back there be no online business .

i no it sounds a lot of money, but it the going rate in web design firms .

only a guide.

ps.
most seo exspert charge £80 a hour in uk firms.

You gotta do your own math based on how much work/hours and know-how it takes.

Recovering a site is not a guaranteed task. So you may want to ask for a reward based system and get paid only if you do get it back.

Just to be clear. Ive reinstate website in full working force and rankings the website.
My fee because was risky project was 500$ per month for max 4 months.So they take risk and for 1.5k for 3 month we manage to do the job very successfully. The owners agreed if I pull out this job that I will get reward.
My per project fee is 1.3k per month.