Haven't read the book, obviously, and I assume he gets into the detailed explanations, but the "value" of what one gives/gets cannot always be reduced to monetary quantities, IMHO. Nor can all "gifts" even be considered to have been offered in an expectation of some kind of "payment." I can agree that a basic definition of an 'economy' involves providing a service that has some monetary value agreed to by both parties, but translating that into 'giving' and 'receiving' "gifts" seems to be pushing the analogy a little too far.
The problem, IMHO, is when outside parties start manipulating he transactions that end up favoring one side or the other. Of course, that manipulation creates a whole 'economy' of those who seek to justify the perceived and actual unbalance of services and payments. Namely, a very large segment of the 'justice' system.
So, things are not always as simple as they seem?