Apart from the keeper from Norwich most of the players they signed from Non-league. It doesn't answer your question but my guess is not that much.
I don't know how it relates to what our guys are being paid, but IIRC at least a couple of the players Peterborough signed from non-league are on between £3k & £5k a week.
Ans as I've said before on here we should get Keith Alexander as a scout, because it was him that brought in most of the players from non-league.