Digital BW, The Print

I guess there are a lot of variables to determining how far an ink cartridge will go (paper 
size, amount of shadows vs. highlights (amount of black used), etc.) but can anyone give 
me a guestimate on how many average B&W prints one might expect to get out of a 
standard inkset, say for an Epson large format printer; or can anyone tell me what you get 
out of yours?

I really can't seem to find anything on google that addresses ink capacity, and how many 
prints (or how much paper it will cover) they will make.

Any advice is appreciated.

Thanks,
~Joel