Would you pay to listen?

I have an untrained palate but still enjoy good food. Cost forbids me from indulging except when there's a coupon.

I think the fee at a hi-end shop would be simply to dissuade the lookie-lou types.
That may work against these stores, long run. I heard some real good stuff a long time ago which while I was ignored in the store (obvious broke kid) was still pretty neat and sort of made me set my course to eventually have some nice stuff. If I had to pay....even 5$ for 'entry' I'd not have done it.

Also, doesn't selling a ticket change some of the legal relationships?

I just re-read my early post to this subject.

I'll reiterate but rephrase. Casual drop ins would be discouraged by what basically amounts to an admission ticket.

IF the store had a dedicated room with 'the really neat' system which you had to pay to hear.... but the rest of the store were open/free/accessible? That would change the balance. 'Show' the system and charge. Tubes / media / floor space cost a bundle.
BUT:
In order to attract new listeners, you have to be able to SHOW people it is better.
The BOSE store I went by yesterday had a good walk-in trade. People talking tech with SALES guys, not necessarily interested in the best sound or interests of the customer. IF the Bose store charged even 1$ to get in, many would walk on by.