> Would be curious to see numbers on the bigger items. Have you used FBA?
Yeah, I've done enough FBA to rank somewhere between a serious hobbyist and an actual lifestyle business.
There is a sweet spot. If you're selling lightweight crap items, even the small shipping and fulfillment costs still tend to dominate. If you sell huge stuff, the shipping will bite, but not as bad as you'd expect -- Amazon has very good rates. The big problem for bulky items tends to be warehouse fees, and also the logistics of getting it to the FBA warehouse in the first place.
I'd say around 1 cubic foot is exactly where you want to be (with the dimensions carefully chosen to keep you in a favorable category, of course). I believe 18"x14"x8" is the biggest legal standard package.
Somewhat counter-intuitively, if you miss that standard cutoff, you might as well go big (3+ cubic feet) since you're paying the same oversize rate either way, the only drawback is warehouse costs. There's sort of a no-man's-land in between toaster-size and microwave-size.
Anyway, here's the actual fulfillment fees, if you're curious (notice how reasonable the rates are in the "Large Standard" range):
On these items Amazon fully realizes they can charge 90% and the seller is still making a profit, so they do.
If you're selling appliances or TVs or computers the % is not nearly that bad.