I'm assuming that by selling you're referring to cheapest 07 gold Sites. Contrary to popular belief most RS Gold Sites are not "farming" their own gold. They do not have a group of unpaid employees who are glued to clicking on an Coal rock to make cash. Instead the majority of Gold Sites buy the gold from other players, and then sell it for a profit.
The RSorder site is one of the "GOAT" RS Gold Seller. He's been running a Gold site since February 2007 more than 12 years ago. I'm certain that he buys gold from major stakers as well as various other companies, and sells the gold on his website. This is the way the business operates, and it isn't logical to employ individuals from third world countries to run a "goldfarm" producing between 100 and 200k per hour.
Be on the lookout for Chinese websites like the ones that have been featured in this thread. They usually employ more dangerous methods of earning gold, like botting. They also frequently advertisements in-game with bots that draw a lot of scrutiny from Jagex and can also ruin the game for all players. If you plan to purchase RS 2007 gold or osrs pking accounts, never be a supporter of sites that are spamming in game.