Many developers have recognized that “play as much as you like” is leaving money on the table, while “pay as much as you like” directs your efforts away from the unemployed and towards capturing as much consumer surplus as possible.
WoW quietly became a came with a cash shop, only the cash shop offered account/character services rather than the usual cosmetic items, bonus xp, and sometime uber loot. WoW has officially started its cash shop. The Lord of the Rings Online™ has started with the adventure pack, DDO is now a F2P (free to pay, free to play) game, but I don’t recall hearing any RMT for Asheron’s Call. Most of the recent releases have their cash shops built right in, and others are adding them. The more unfortunate games are adding core services and things that were supposed to be part of the basic package as cash add-ons. Wizard101 has been bulking up its shop.
Which games are left without ways for you to spend dollars beyond a monthly fee?