If you buy insurance then it would cost an extra ~$4 or so (this is assuming the value of the coins is under ~3BTC). If you want signature confirmation of delivery then it would cost an extra $3.10 (iirc).
FedEx and UPS are going to be more expensive.
The value is less than .1 and Im dealing with a very trusted user and I have many more in case for whatever reason they manage to 'lose' it from point A to point B. 6$ is roughly half what I charged for shipping and more than 25% of the coins value. I really assumed that I could ship it domestically for less than $5 anywhere. Ill just bring the coin into the P.O. and talk with someone there. If anything not recommended above is available I will post the method. Thanks guys.
In theory you could put it in an envelope and mail it as a letter however I would not recommend doing this because I don't think you would be able to sufficiently package/pad the coin.
I was in able to buy a padded envelope for 1.59 and it was 2.55 to ship 3 day from USPS w tracking. This worked well for me just remember if using this for reference this coin had a very low value. If it were worth any more or if the buyer didnt have such high trust I would have had to use a small priority box for $7 +tax. Thanks guys.