I may have posted this one before.
JB Hi-FI 2.65% surcharge for using Amex! Seiously? That is a joke.
Seems to change depending on the store, I've seen as low as 1.95%. The part that gets me is they rationalise it by saying it's the premium compared to other cards. Which would suggest they are being charged 3% or more by Amex.
If you use JB Hifi online you can pay with PayPal and use Amex that way, but most likely will incur a postage fee.