Yeah, I've spent between $20 and $30 on PL. That's all.

If you're really strapped for cash, just buy the campaigns like Varking said. Don't spend Plat on equipment, because the loot you can earn is better that what you'd buy. Don't spend Plat on gold, vanity items, stash slots, or Halloween packs. Just buy the campaigns.

If all you buy is the campaigns, then PL is very affordable for an MMO. It's still a bit pricey for an iPhone game, but it has a lot more content than any other "standard" iPhone game.