Comment by Aqueous

Issuing stock is not the principle way they maintain positive cash flow. The float between the time their customers pay them and the time they have promised to pay their vendors creates enormous, ever-increasing operating cash flow:

https://hbr.org/2014/10/at-amazon-its-all-about-cash-flow/

They are essentially borrowing from their own customers (or maybe more accurately, vendors), at zero interest, to continually build the business.