Correct me if I'm wrong, but BA's exorbitant taxes/fees become somewhat more palatable when using the miles to fly BA in J or F as opposed to Y. That is, while they may be even higher for J or F (or are they?), they still are relatively cheap compared to the $$ value of those tickets.

I'm not trying to justify BA's approach here at all. Just trying to clarify how to extract the highest value if you can't or won't want to use the BA miles on other OW carriers (such as if you're using the miles for the 2-for-1 BA mileage award deal).