Joe can make special area for players who pay-for-play, not use current maps, where are best monsters and ores to earn experience and cash.
I did construct such a place ... it's called the Lava Mountain. And the only reason free players have had access to it is because of a two year delay in getting the pay-to-play online.
In the entire history of Queville, not once has it ever made a profit - Google Ads have never covered the hosting expense. Not to mention all the computers, software, and hardware I've bought over the year. All of your "hard work" was paid for by me.
And if someone is going to spend all of the time using my resources to be able to mine Lava Ore, then I don't think asking them to pay a little something is asking too much.
If not, they can always obtain Lava Ore from someone who is paying. To me, this is more about providing the paying members a perk than restricting free players. They are paying your way, so giving them access to more resources is very fair.
And while Queville will be "free to play forever", that doesn't mean the entire game will be free - a members area has been in the works from the very foundation. There is still a lot of content available for free even without the Lava Mountain.
It is my opinion that Queville is one of the best valued games online.