I've been using Epson printers for almost 12 years now and i can tell you that the prining costs are really high if you do artwork on your printer.
The ink consumption is incredibel much.
On my Stylus Photo 900 I need new inks every 12 to 15 pages full format color DIN A4 sized.
This ends up @ roughly 50 EUR for max. 15 pages = 3,30 EUR / page.
I am now choosing between the HP Designjet 90 and 130 because I've seen some prints and I've seen some quotations stating that the printing costs on the Hp 130 / 90 are less then half the cost @ comarable printing result or even better @ larger size compare to my entry level printer!!
So I think if you go for a semipro printer @ HP or any other company printing costs might drop. Specially @ the 30 / 90 and 130 series for HighEnd prosumres