yeah, I think it's a very fair idea...great principle.
'Morning Sir, how may we help you?'
'Well, I paid for a TV on your website for £250, I'm just here to pick it up as arranged?'
'Of course Sir, it's in Electricals on the second floor'
'Great, I'll nip up and get it'
'Not so fast Sir, we plan to upgrade the escalators and add an extension in maybe possibly perhaps five years time, you'll need to pay a £5 fee to cover this'.
Shove it!