Whoops, miscounted there. But yeah, I already said right there in my post that it’s not really relevant right now, considering the competition between shops is at the maximum rank for all three merching classes. Not sure why you’re bringing that up again.
Here’s a better way of looking at it: how often do you drop by a Pardoner or Squire shop to put on some buffs? I’ll usually use a shop maybe once or twice a day, if I’m planning to do some serious grinding or preparing to fight a World Boss. If someone sets up a shop outside a dungeon or by a popular grinding spot, why wouldn’t you want to buff up for faster grinding? If there’s a Squire repair shop right next to you wouldn’t it be better to just use that instead of going all the way back to town, even if Squire is slightly more expensive? Squire and Pardoner profit off convenience, which is why they can make so much without needing high prices. They’re always in demand somewhere.
Now, how often do you have to roast a gem? Personally, I’ve used three gems total, none of them roasted, because I don’t have endgame gear yet and there’s no point in putting so much funding into an item I’m going to throw away in a handful of levels. Gems in general are already costly and tedious to level and socket into gear, it costs a chunk of silver just to open a socket to use and levelling takes dozens if not hundreds of gems/abrasives to reach something high enough to justify roasting it. Also, you only need to roast a gem once, ever, compared to buff shops which can be used over and over again every hour or two. Roasting is for min/maxing gear, which just isn’t something you need until you’re deep into the current endgame with high-level gear that you plan on keeping for a long time.
Do you really expect 1000 people to need to roast gems in a single day? Or even a single week? Maybe if you undercut everyone by 10k you might get a few extra people jumping on the deal, sure, but you’re never going to get numbers that could compare to Pardoner or Squire. There’s a reason why you don’t see a lot of people bothering with Gem Roast shops compared to the 4657345 Pardoners/Squires lurking in ch1.