Here's a little update for US sellers.
USPS wanted $100 and $120 for a frame box and full bike box respectively. Both were headed to the west side of the country at Parcel Post rates/speed. Usually Priority is up to 108", and PP is up to 130"--but it turns out that if the box is over 108" even for Parcel Post there is a significant surcharge---like, 2-3x cost. This was new to me. Maybe my branch was crazy?
Ended up going to FedEx. I insured both and request a sig, but the frame only was $67 and the whole bike was $99.
I have accounts with USPS, Fed Ex and UPS...figure all my shipments at home and just drop them off. I've been doing more parcel post and paying a tad extra for proof of delivery. I've shipped a number of complete bike in the US for $39-65 by parcel post. I also send "return shipping labels" to be printed by the seller and put on the box when I buy things. Better rate to myself that way.
Yes, I shipped an entire bike, shipped with $1000 worth of insurance to the West Coast from NYC for $56.00, via Fed EX. UPS wanted $83, and USPS was $97. I remember shipping a frame via USPS priority mail for $26, just four years ago. Things have certainly changed.
Though, regarding USPS- some branches are better than others, or the workers less competent.