Most big MMOs have membership or subscription like osrs and wow. Its not that expensive however it adds up if every player buys it. For 100% f2p players there should be an option to buy it from other players with gold, as f2p you don't contribute to game development so in return you pay with your time. And before you start yelling at me "P2W, P2W!!!", thats coming from a player who has played for almost 10y and has bought plat only once xD The reason I would love to see this system is that more money = more content (hopefully).