A lot of times Regional A and Regional B will save money. Just sucks not all payment platforms recognize it, so sometimes getting a quote is difficult, and if shipping to a farther-out zone, you can lose $$ over shipping in a Medium flat-rate box. I think eBay recognizes A and B now, but PayPal still doesn't? I prefer shipping through PayPal because it's just all-around easier.
I found a great trick to get things out super-cheap and fairly fast w/tracking recently if it's less than 1lb in weight. You can shave off a few cents more using PayPal assuming you have a PayPal account.
Login to PayPal via the shipping backdoor - this lets you ship in cases where someone pays F&F or didn't pay you via PayPal at all:
https://www.paypal.com/us/cgi-bin/webscr?cmd=_ship-now
After you login, you'll be prompted to input the receiver's address and email address - if I don't have their email, I'll use one of my throwaway accounts.
When you get to the speed/service selection, choose First Class package (3-5 days), then choose "large package box" and set the # of ounces the package is (up to 16). I sometimes ship in padded envelopes also, but still chooose 'large package' in shipping options.
I've sent a bunch of freebies out recently this way to pay-it-forward on something awesome
Mad Honk did for me last year and I never paid more than $3.50, most people got the item within 3 days - some Park cone wrenches to skyerocker to help with the burned down shop, Simplex cable guide to cqlink for his PX-10, Simplex seat binder bolt to cudak888 for his Leo build, some misc cyclometer parts to crank_addict, cotter pins to orcas_island, etc...all under $4 and most under $3.
This may already be common knowledge for some, but it's new to me. I'd been having a hard time getting smaller packages out the door for less than $6. As long as the grand total with packaging doesn't weigh more than 1lb - seems all of my 5-6-7spd freehweels are a couple ounces less than a pound - shipping is pretty darn cheap.