Hello. RAT is a consolidator. Like any independent business, they set their prices according to what the market will bear. Sometimes consolidators will have fares lower than the carrier. Sometimes they will be more. (Many of the consolidator fares to Europe this summer have been higher than the carriers) Sometimes the class of service ticketed by a consolidator will allow mileage accrual. Sometimes it will not. Sometimes the tickets sold by the consolidator will have more strings than the fare sold by the carrier. Sometimes there will be fewer. They buy seats in bulk and gamble that they can sell enough of them to make a profit.
Say that Supermarket X advertises that they have the lowest prices in town. They sell tomato soup for $.69 a can. I go to Supermarket X and say "hey, if I buy 100 cases of tomato soup, will you sell it to me at $.59 a can?" Like any smart business, Supermarket X agrees to the sale. No advertising costs, no stocking costs, no bagging costs.
Now I set up a stand across town and sell tomato soup. Supermarket X has no control over my pricing. I'm an independent business. I sell tomato soup for $.64 a can. Since the margins in groceries are so slim, if Supermarket X lowers its price to match me, it would loose money on every sale. But it wants to make sure it has the lowest prices as promised. So it stops selling soup to me and customers loose the option of buying soup at $.64 a can.
You can buy soup or plane tickets at $.64 and be happy, or you can b**ch that Supermarket X or DL isn't keeping its promise of lowest cost and watch your total price go up.
Be thankful that consolidators exist. In the days of regulation, they were mostly illegal. You have to shop around and look at fare, class of service, mileage accrual, change penalties, etc, and make the best decision for you. Sometimes that means that a consolidator is best for you. Sometimes it is not. But expecting DL, or any carrier, to match every consolidator fare is absurd.