As of right now everything I'm producing tends to fit inside of Size 5 (10.5" x 15") padded mailers and those tend to work out just fine. I've got one more box of them to go through and I'd like to look at what other options are out there. My finished goods are flexible and lightweight and looking at how some of the mainstream bag companies are shipping their goods, I've seen a number of them using these poly mailers
https://www.amazon.com/Metronic-Envelopes-Shipping-Waterproof-Tear-proof/dp/B00OLOGXWU/ Which are 1/4 the price of the bubble mailers and seem like a good value for shipping softer stuff. I've even gotten a Timbuk2 backpack direct from them shipped in one of these types of mailers. Theirs had some nice artwork on the outside of the packaging that was a complete bike map of San Francisco - nice touch.
Would love to hear what others are using to ship their finished goods, and whether domestic/international shipping plays a role in what you choose. Thanks!