Sounds reasonobubble to me. My old 1967 172 is leased out at a dry rate that makes a reasonable comparison with the sort of costs you're talking about.
Important thing is the state of the group's finances and the personalities in the group - and how you fit with them.
Engine's (roughly) halfway through it's life for a public cat a/c - but if it's on private cat then it can be extended. Ask about their engine kitty and approximate annual hours flown for the a/c - hopefully, they'll be building up a fund at a rate commensurate with both.
Not sure on the engine for this type, but some engines need top overhauls halfway through their life - not as a regulation but as a matter of course as components wear.