craftgrrl | A question about boxes

Those of you in the US who ship out your items in smallish boxes (~6" cube or so) in some not-super-small quantities, where do you buy your boxes? I have a place I've been using for 3 years or so online, but the shipping lately for 100 boxes is punching me in the gonads. And yeah, I do prefer new boxes, not used - looks nicer to the customer and has better durability - otherwise I'd be scavenging. I tend to ship first class and I'm not okay using the USPS boxes that are meant for Priority as some have suggested to me. I am A-OK with paying for mine! Just wondering if there are reliable places that offer less expensive shipping than the place I use now.

So this is not text only,