Here's the thing - a great many "ultra luxury" brick and mortar stores run at cost, or at a loss. Although they will attract wealthy clientele who make large purchases, the big-ticket items sold there barely, if ever, pay for the cost of having them on display there. Even the wealthy clients mainly only go there to look through the collections in-person and will then make custom orders.
A lot of the time they're there so that people who can't afford a coat or a gown are encouraged to connect with the brand identity, so that they then go on to buy a wallet, t-shirt, lipstick or perfume bottle from one of their cheaper diffusional lines.
If you can't afford the stuff on the rails at Dior, then, believe it or not, you ARE the main target audience. It makes sense to dazzle you, sure, but alienate you? No.
I've been a shop assistant in these kinds of places, then trained and managed them. The first thing you learn is that you can never tell how much money someone has until they've handed their credit card over the counter. Snobbery was never a part of what we did because it wouldn't have made any sense. I'm not saying it never happens, but it would certainly never happen for long if a store wanted to survive for long. Nobody got "subtly chased away". The more feet through the door, the better.
Besides, the people who wear their fancy clothes, heels and makeup while out shopping are usually self-conscious middle class people. Perfectly lovely, but are usually, like me, only there for small gifts.
If you "experience" snobbery from sales assistants often, I suggest you watch too many movies and have an underdog complex.