VooDooPC
Priority is around $7 and First Class is around $3 for packages under 1lbs. Both have tracking. I think your post office is charging you too much.
That $7 for Priority is only if you use the USPS Priority Mail packaging and depends if the Powerlink will fit in their box. The small size Priority Mail boxes ($6.80 shipping when paid online, which is cheaper) wont even fit a Samsung EVO SSD in retail packaging, so the next step up is Medium box which is $13.45. ALL post offices have the same prices.
A standard 12.5" x 9.5" bubble envelope I sent Priority Mail a week ago cost $8.40 when paid online, and that was to a nearby state. If you use one of the USPS bubble envelopes it's $6.80.