They're not paying anything extra if they intend to buy the dry suit. A drysuit is definitely something I would buy in store.
Except when you go in and find they offer only a couple brands and those brands do not have mode/size that fits you. Or you find that the shop does not have the size you want in stock and you are ready to buy so you go a couple towns over to the next dive shop and buy from them because they do have what you want in stock. As a customer, one should not be in the business of quizzing shops about their stock levels as the first part of the engagement, and if I am required to pay 20 euros up front for the privilege of trying gear on in their shop one of the onuses that is put on my shoulders is to question their stock levels at the outset of the engagement...this is not a typical responsibility of a client. Nor is it typical in any other retail clothing situation for customers/clients to pay upfront to merely try on clothing items.
If you are going to sell clothing, undersuits, wetsuits, drysuits, booties, etc, then it is should be expected that your product will be tried on by your clientele, if you don't or can't account for this then clothing retail is not a business you (proverbial you) should be in.
This business practice adds no value to the transaction for the customer, adds a false sense of guarantee of sale for the business, and while in the short term they will make 20 euros, in the long term they will lose much more as it is not a business practice that creates customer focused value.
If you are having problems competing with internet sources for the same equipment, you should be looking at ways you can provide value to your customers....not everyone shops on price alone.
Look at DRIS as an example: with every drysuit they offer a"lifetime guarantee" free of charge which includes free leak tests (1 per year)....this adds value even though they know that not everybody is going take advantage of it...for their suits sold online or to out of state customers the cost of shipping each way is a responsibility that belongs to the customer but if you want/need your suit inspected they will do it free of charge....in turn they will have your suit and can offer to repair it for an agreed upon amount which is potential revenue. Value to the customer, potential revenue stream for the business, equals win-win. The client incurs no obligation to engage and whether they use it the guarantee or not, and I bet most don't (though I could be very wrong).
The above is an example of a perceived benefit. Why is it a perceived benefit? because if you actually have a leak you would probably send your suit to them for repair anyway and they will have to leak test the suit anyway to find and evaluate the area that needs repair. If time or shipping expense is too great then one will typically forgo the "free" benefit and look locally for a repair service...the benefit remains but is not taken advantage of.
Many business fail because they are primarily revenue driven not value driven. Revenue driven customer interaction is typically a one shot deal...if the customer retuns it is still driven by the immediate need and is a one shot deal, the customer is only buying from me (proverbial me) because my price and/or availability is better than my competition. In a value driven business, the business is seeking to establish customer loyalty, i want that customer coming back to me to meet their needs, I want them to think of my business as their primary source for satisfying their wants and needs in that market segment, and I want them telling and bringing their friends and family to my business as well....and when they do I want to ensure that the quality of experience lives up to what the initial client pitched to their friends and family to convince them to walk through my door.
I have been a part of the cycling and skiing industry much longer than I have been in the dive industry, and I can't even begin to count the number of shops that have vaporized because they could not sustain their business, and yet there are shops that have been around for decades with the same owners or owned by a younger generation of the same family...the unique thing about those shops is not that they offer good pricing, it is that they offer "great value".
-Z