I see geekvape and others pumping out plenty of rda's. Maybe because I buy online and not from brick and mortar stores. BKTOAD may be on to something, stores want a level of dependence and return customers. Those who get in the habit of buying coils generally come back to repurchase. Wire and cotton can be purchased plenty of places and generally for less, in combination with the regs about stopping building in the shops.
Even if the regs weren't in place, it's easier to hire someone at a register who can simply hand a package with little to no knowledge other than 'yes, these coils are compatible with your tank, here's a package'. They don't require people who know how to build or set things up.
B&M's, not sure what the deal is. If they can't get things for wholesale or if wholesale is basically what other vendors are offering people online. It's almost as if they buy things at full retail then slam a markup on it making the price less than competitive. Kits are improving, they're including multicoil replacement heads and things but I don't think it's a replacement for building.
I really can't say why, maybe it's legit based on limited buying power but I've seen 'mom & pop' translate to 'overpriced' like it's a justification. Granted bigger outlets like walmart or chain grocery stores have more buying power but they're all similar. A good example are local 'farm & feed' stores. You can grab a snickers bar from the grocery store for around $1. The farm store? They're selling the same size candy bar for $1.89. On top of it they're old and dusty like they've been around awhile. Go to buy other things like motor oil and they're charging $6-7 for the same quart I can get for $3.89 up the road. That's a hard sell, call it 'mom & pop', 'local' or whatever but I don't like getting jacked either. Vape shops seem to be the same way.
Eciggity is another online u.s. vendor (hawaii based, fast shipping though). I don't know that they have the absolute cheapest prices, they have several rda's though. Probably 50 or so different rda's, both genuine and some clones (clearly marked). They've got the tsunami, regular, 24, with and without window, the doode (squidoode's), troll v2 standard and 25mm, sapor v2, recoil, peerless, lynx, lush plus, druga etc.
https://eciggity.com/rebuildable-1/
They've also got a few other things, a bit of wick, wire, batteries, chargers. A little limited but those are things that can easily be gotten elsewhere. Japanese organic cotton is cheap and easy to come by on Amazon, a lot of folks get their wire from temco direct I believe. Batteries and chargers can be gotten from IMRbatteries, Illumn.com or other similar places.
For me, this is my vape shop lol. Between lots of helpful folks on this forum, many are builders, vendors, reviewers. Once in awhile reddit or ecig forums but 95% of the time it's here. Discussions about new things, what things work or don't, good sources for various stuff whether juice, diy supplies, wick, wire, batteries. The few local b&m stores around me look like hole in the wall places and doubt they have a 1/10th of the knowledge of folks here do.