"John Rumm" wrote in message
o.uk...
On 29/07/2018 14:05, Jim K wrote:

Why would a shopkeeper or tradesman accept less than the item/job
owes him?

Because they have assumed a certain transaction cost and built it into the
retail price. That likely includes accepting payment in forms which come
at a cost to the trader - such as credit card fees on each transaction. If
you come along and elect to pay in a way which does not incur them some of
their budgeted fees, then they have some more negotiating space.

But the merchant card fee is never anything like 10%

Much the same when you offer to buy the whole box rather than a one off...