I've sold a bunch of chips lately and have used this technique without any problems.

1) Cut about 1" off the side of a bubble mailer so that it will fit in a regular business 9x4 envelope
2) Put one or two chips in a 2x2 flip, put the flip in the bubble mailer and tape close along the cut edge
3) Address the envelope and put the bubble mailer in the envelope
4) Seal the envelope and secure with long piece of shipping tape along the seal, the tape prevents tampering
5) Bring the envelope to the post office and say that it is "Non-machine Readable"
6) Cost today, new rates, for 1 chip was 70 cents. Last week it was 71 cents. Saved a penny.