Actually, that's a bit misleading. IIRC, it was the opposite, they were charging everyone (as in higher fares to make up for revenue lost through the seats they had to take out on each flight). That's why it didn't work, because when Joe traveller and TA went to book flights, AA would never show up on top, and therefore bookings fell, as most people book based on price. E+ on UA has survived because rather than bringing up the price for all, it served as a benefit for loyal customers, and an upsell opp (not at first, but eventually) for those who aren't elites, allowing UA to get incremental revenue.