afaik, different countries have different merchant agreements with the cc companies, but in most countries (including usa):
-Merchants cannot require minimum purchases to use cc.
So if you visit those chinese restaurants or pizza places that require $10 minimum for cc charges, that technically violates their merchant cc agreements.
(In BBO's case, the product, BBO$ is sold in units of 10s, so it is legal, since the product is 10 BBO, 20 BBO, etc)
-Merchants cannot charge more for cc usage. So they cannot say use cc, this item costs $10.50, use cash, item cost $10.
However, it is legal to offer cash discounts.
A few countries have different prevailing merchant agreements, but most of the developed world has the same one as this.
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There's a cost to cash too, as mentioned by some posters above. Cash crimes, having to visit places to deposit the cash, some lost opportunity cost of money, and I guess printing the bills is more costly than plastic cards that last longer? (And of course, the amex black card is made from titanium, which should last a very long time!)
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Josh, it's generally accepted that Amex charges higher merchant fees than visa/mc. Perhaps during visa/mc's early years they could have offered special promotions to push their product? Wonder if that's legal actually - isn't that kinda product dumping? To use their profits from other merchants to subsidise a foray into another market.
Please don't give banks more ideas in charging cc users fees, I love my frequent flier miles and want them for free!
"More and more these days I find myself pondering how to reconcile my net income with my gross habits."
John Nelson.