On this topic, I just checked the fares for one of my earlier BF sale reservations:
EWR-TXL end of July, using the same dates I've already booked, the BF Z sale fare of $ 1626 is still there. But what's interesting is if someone did not know about the sale, and was looking to book an 'upgradeable' fare and use miles + $$ for the BF seat, on the exact same dates/flights-- they would be faced with paying $1766 plus 40,000 miles and not being certain of getting that BF seat !! Right now the cheapest coach fare is $966 which is an I fare outbound (upgrade fee $450) and a B fare on the return (upgrade fee of $350)