I want to know the range of interest rates (fixed only) that American
Express charges its cardholders for regular revolving credit. I am not
interested in the rate charged for revolving credit on travel expenses
only, for the pay-in-full cards.

I want to negotiate a lower rate with them, but not if it's a total
waste of time. I have not found any web sites (blogs, gossip, etc.)
with this information, though I assume they exist; I have only found
teaser rates and new-card rates.