I was told out here that it's the bubbles in the mailer that trigger the Small Packet Rate, minimum $3.95 and it goes up depending on destination. This does include tracking, however. Although I've found that buyers don't really care about spending the extra for it.

I went with the Cuzzin Reggie method:

Bought a box of Safe-T-Mailers from the firm in Brooklyn - corrugated paper with some special gluey stuff on it - put your chip or coin on the gluey side, fold it over and it seals up. But not a real sticky seal, so the recipient can peel it away and get the undamaged chip out. Put that in a #10 (or smaller) envelope, place it in the middle of the envelope (per my local postal clerk) not at one end or the other, tape the cardboard to the inside of the envelope. Mark the envelope "Non-Machineable" and attach a Dogface Butterfly stamp which is the 80c or 90c Non-Machineable first class "penalty" rate.

Drop the envelope in a mailbox at the post office (don't hand to a clerk unless you want a California Lecture as to why you shouldn't be doing this) - and run like heck!