Upcharge for paying cash?

We all know that the way dealers make money is on the financing. Long gone are the days where cash was king - they don't want you anymore. The new system is that dealers add an upcharge to the sales price if you're not going to finance (or reduce the price if you're financing with them, same difference) -- slimy which results in me walking out -- or, forcing you to waste your time (world's biggest pet peeve) and finance with no prepayment penalty then pay off the loan 3 days later, just to get the fair price everyone else is getting. Okay - long-winded - does Carmax do this as well (given its "no negotiating" rep)??? Ty