It's not the same thing. Fare classes available overlap is the best way I can put it. In other words, seven different economy fare buckets showing 9 does not mean there are 63 economy seats available. In the extreme, it might mean there are only 9 economy seats available and they are willing to sell them for seven different combinations of prices and fare rules.

I couldn't get grease monkey to work, FWIW. Surely my problem.

Of course there are loads of variables that wouldn't be accounted for. But I'm pretty sure this data is not available anywhere, so my idea would be a step forward.

Edit:might be a step forward.