There is something in that. You have to establish relative worth in order to assign a money value. That is, 1 pig is worth 10 chickens, or whatever. And 1 house is worth N pigs, and so on, assigning relative value to services also.

It makes sense that relative value is established first by barter, but it is not such a stretch to think that people could work the same out relatively quickly, once the money value of one common thing is established.