[st2p]

Sharing expenses is compensation and the reg alludes to that fact in part (a) and by virtue of the list of the exceptions to said reg. If you really need a concrete example that includes the "compensation or hire" verbiage look at exception (b) of the reg.

(a) Except as provided in paragraphs (b) through (h) of this section, no person who holds a private pilot certificate may act as pilot in command of an aircraft that is carrying passengers or property for compensation or hire; nor may that person, for compensation or hire, act as pilot in command of an aircraft.

(b) A private pilot may, for compensation or hire, act as pilot in command of an aircraft in connection with any business or employment if:

(1) The flight is only incidental to that business or employment; and

(2) The aircraft does not carry passengers or property for compensation or hire.