You're still not being clear about your own intentions, which makes the difference. I could go to American Top Team in Florida and sign up for classes, and the price wouldn't be much different from what most gyms charge. The same could be said of Miletich, Team Quest, American Kickboxing Academy, etc.
The pricing is usually different if you're an actual professional fighter and member of their fight team (different from just being another guy who takes lessons at the gym).
Here's ATT's fight team. At this point you get more of their attention because they're actually training you for a fight, and probably cornering you too. I know Marc Laimon at Cobra Kai gets a cut of your fight purse when he's training and cornering you.
And as for that gym in Scarborough, I don't know -- I'm skeptical. Their site talks like an infomercial, and when any credible MMA/BJJ gym in town charges around $100 a month, $19 sounds too good to be true (I say you get what you pay for, you know?). If you check them out, come back and let us know how they are.