Yeah, considering the prices USPS has on those flat rate boxes, it just doesn't seem economical to use UPS.
Anyone that uses USPS for shipping pays the same as the next guy in line.
With UPS you get discounts depending on how many packages you send a week/month.
(no I'm not affiliated with UPS or USPS)
Flat rate USPS Box is $4.80 with delivery confirmation.
UPS with real tracking, confirmation and $100 insured is $4.00.
If you go to one of their stores or a "Mail-Away" place you will get published rates or higher. I'm guessing $5.00-$7.00
I do tend to use USPS when sending out things I have sold personally as it is usually easier for the receiver.
For our business though, I wouldn't even consider USPS as an option because of the limit of .lbs, insurance, tracking etc..
For an individual, it is the best route.
All-in-all I've had good luck using both.
Only 1 indecent with either one and both were taken care of.
USPS damaged a package almost beyond recognition and ruined the contents.
UPS lost a package, never to be found again.
mike