That's a big printer and maintenance, just like our cars is never as cheap as we want it.
Link -> http://fineartgicleeprinters.org/Epson_wide_formatinkjetprinters/Epson9000_wideformatinkjet.html
If you can find the part you want, then go for it.
Hi! I got a question about Epson StylusPro 9000 printer, my maintenance tank needs to be replaced, but Epson is trying to charge me $500 to replace it. It's an old machine, also the tank itself costs under $100 which I can afford. I was wondering can I replace it myself, is there any instruction manual that shows me how to install the tank myself. Or anyone has a similar situation, who can give me some advice.