USPS Priority Mail gets ridiculously expensive when one dimension goes over 12" (unless a relatively thin package). UPS is better if over 12" as a rule.
Technically, you're not getting 2 shipping from Amazon for free - you or someone who "sponsored" you paid for Prime. But your point is well taken. And both B&H ship free if the order is over $49. Even Freestyle, which charges for shipping, is cheaper than I can ship it for.
I think the only way to ship what you want economically is if someone has pretty much everything you want. I'll send you a private message.