Charging A Fee To Demo An Amplifier In A Brick & Mortar Store

I Saw a pair of pre-owned tube monoblocs for sale on an onlline forum for around $17k.
The seller has a retail store for hiigh end audio. The seller mentioned that there will be an up-front fee for the demo if a prospect comes to the store the amps are not purchased. The demo fee may also be used for credit towards any purchase in the store.

This is the first time I’ve ever heard of this. Is this now a common occurance in high end audio stores? I sent a note to the seller asking what the demo fee amount was....two weeks and I didn’t get a response.

Does anyone know what amount of fees are charged for a demo?
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One thing to consider, with 800 hours on the tubes, its going to cost a few grand to retube the units if you buy them from ARC.   I think why they have been sitting for so long is huge the price to retube them when it is needed.  It is a BIG expense.  I hope you live in Alaska or Siberia as those amps will probably keep your house hot year round.
I was also fortunate to run a high end store w no commission sales team...

when a customer came in and after asking them “
how can I help “? Sometimes they would reply “ no, I am just looking “
I always said in reply “ when I go to the bookstore I tell them no thank you I am just listening “

tended to break the ice, music was next !!!!
Just to be clear, the $500 gets you a store credit that can be used towards anything else the retailer offers.  Quite often when I visit an audio retailer and audition something, I typically purchase an album or 2 as a way to show my support and appreciation for their time.  
Also our local Porsche dealer required a signed purchase agreement to drive the big HP turbos.... wishing I could get one for $17 k.... tubes or not :-))))
For one the guy is a jerk for charging and just reduced his chances of selling by st least 50%.  I sold audio for years ,never a charge .
what is the $$ amount out of curiosity ?