Strapi v3 to v4 migration time estimate

I have a potential client that would like me to migrate an app from v3 to v4 (database and code). There are about 25 collections and several custom api andpoints. Also 1 custom plugin for importing / exporting data.

I’ve migrated small blogs with little issue. So I guess my question is, if you’ve migrated a medium to large Strapi app from v3 to v4, how long did it take you? Would an 80 hour quote sound ridiculous?

Thanks,

Richard W