Costed it out today and the rate for stuffing the envelopes ( you supply the envelopes, inserts and the labels and stamps) is around $50 here per thousand. Will be a quick 2 day job per thousand for the one contract packager I know, he makes most of his business by being one of the few who will do loop stapling in small lots. The loops are bloody expensive, along with the special staplers that do with them. Works out to about $1 per flyer to do.