There are also restrictions on lifing of parts, sourcing of some non-critical bits, etc. So, in taking an aircraft that's been private for some time to public, you may find yourself replacing (at considerable expense) quite a lot of apparently perfectly serviceable aircraft parts.
Also a lot of minor tasks that on private could be signed for by the owner now can't, so the entire private-cat service history will need reviewing and any number of minor oddments may need inspecting, all obviously requiring expenditure on wages if nothing else.
Not really my area of Engineering, so by all means anybody better qualified correct me.
G