REDLINE MTL TRANSMISSION FLUID BMW MINI COOPER & S, is the transmission fluid that your BMW takes. I have a website that you can order of off and the price for 1qt is $16.95. So I would say that your Mechanic is over charging for the transmission fluid that you need. Here is that link so that you can see how much they are charging. If you have any other question, please feel free to ask. Thanks
http://new.minimania.com/web/Item/NMG7299/InvDetail.cfm
Experienced Auto Repair