The outlay for infrastructure. Previously you had to own your own hardware, get a business class line, maintain it, etc. Now you just rent servers from AWS or another provider. I like to think of it like a ski rental. They build a few extra services on top to make it even more convenient, but the critical part is the hardware.
The part where a credit card is involved. It's not directly renting equipment, it's renting money to buy the equipment in anticipation of earning new money to replace the rented money, but it's isomorphic to renting equipment, which is rather the central point to the idea of capital as marketable goods rather than entailed property (or, commonly, an appurtenance to entailed land) which distinguishes capitalism from feudalism.