I know someone who charges a fee for trying on sports shoes because he got tired of people trying shoes to see if they fit and then buying the same pair cheaper off the internet. Of course if you buy the shoes from the shop, then the fee gets taken off the price.
That is smart. People will pay the fee if they are sure they want to buy that product from the store.
I bought some cowboy boots a while back and I was really unsure of my size (usually you want them a little larger than regular shoes, if they have a pointy toe). I walked into a store and tried on 2 pairs and found the perfect size. They had the brand but not the style I wanted so I didn't buy boots. On the other hand, they had the only pair of laces I have managed to find for a pair of 14-up DMs, so I got those.
(See, when you get people in the door, sometimes they buy stuff they forgot they needed).
I think I might have been prepared to pay a fee (maybe a fiver?) to confirm my boot size as that is the crucial part of buying shoes online.
As far as cameras go, I would generally be smart enough to download a manual before doing the shopping IRL. Nothing beats checking it out in a shop though. Handling is an important aspect.
But that's retail. Either someone has already played with their friend's 5DMkII and wants one, or they need to keep up with the Jones family, OR they're not sure about the product yet. You let them get a feel for it, they might buy it from you. If you can compete with other retailers, you've got an advantage. If you pay astronomical rent, then you're at a disadvantage because your prices simply have to be higher. Several camera shops here (Dublin) have gone bust because they were in very high-rent areas.
I always got taught to 'do it yourself', but I still recognise a useful salesman and don't mind paying a little for their help. It is kinda like tipping. Unfortunately, a lot of sales people these days (in many industries) just don't care for their jobs (and will lose them, given time).