From what I can tell reading around—the options are such:
Membrr - $145, hassle to install, and requires 2 logins to operate, but has many features and gateways.
http://www.membrr.com
Simple Commerce Module - Free, PayPal only, lacks advanced features
http://ellislab.com/expressionengine/user-guide/modules/simple_commerce/index.html
CartThrob - $150, many features and gateways, but subscription add-on is not yet available (beta only).
http://cartthrob.com
Exp-resso - $150, many features and gateways, subscriptions will be added but not in the near future
http://exp-resso.com
Also, there is a system called aMember Pro—which looks very robust, but is separate from EE. They do offer an Expression Engine Plugin, but I’m not sure what that means exactly. I’ll look into it more:
http://www.amember.com/p/