I play Lord of the Rings Online, one of the older mmos still going, it originally started with a sub model, but went ftp with paid after maybe 2 years online. Despite what a lot of people feared would happen, that game has not turned into a monetisation hellscape. Most of the big ticket items in the store are actual content, region packs, quest packs, expansions, or character-based items that give boosts, not instant wins.
BUT they never got rid of their sub options, and gave subs a currency allowance and free access to non-expansion content that you would normally have to pay for. It's not perfect, and they've still struggled to find the balance between paid and non-paid players. Now, LOTRO is actually one of those games that you can genuinely not pay for, because it's not hard to grind in game for store currency, and people do so, to great effect.
I like to compare mmos like LOTRO (and DDO, which is made by the same company), with mmos by Cryptic. Crytpic had a similar start with some of it's older games, but they very quickly embraced the f2p model as it became popular. Their older games retained their sub options, but their newer games did not (they did eventually, but after the damage was done), and those games did turn into a monetisation hellscape, because without the option of falling back on a regular income from players, they began to get exploitative. I played NWO for a few years and got continually very upset at the level of money-grubbing going on, until I stopped playing entirely. It's also upsetting that that game is WOtC's flagship mmo for D&D.
