Not a bad idea. Might save money in the long-run. One idea is to use Starbuck-type coffee holder sleeves to sandwich the chips, or from cereal boxes. .. ... Good for low cost plentiful casino chips.

Bad things about it:
¶ can't get delivery confirmation with letters, and it is often free with first class parcels (like with PayPal shipping labels).
¶ will likely break many types of chips (like vintage clay poker chips);.
¶ sometimes the mail piece will break,.. .... or post office might charge higher rate if it deemed not a letter.
¶ savings isn't tremendous. .. ..... First class 2-ounce letter with postage stamps, including non-machinable surcharge) (no delivery confirmation allowed) -- $0.93. .. .. ...First class 2-ounce parcel made via PayPal label (w/ free delivery confirmation) -- $2.04.

http://pe.usps.gov/text/dmm300/Notice123.htm#1118064

Robert