I use the Epson 9800 everyday, running a fine art print shop. Waste is an important factor to consider. We usually use rolls of 44". The paper that is left over is used to make proofs. For bigger prints we make a small crop of the image on final output size, for proofing on left-over paper. You can make a lot of proofs on relative small pieces of paper.
By "collecting" your print jobs and print them all at once, you can be more efficient on roll paper. A RIP could be of great help in this. If you print more or less fixed sizes, it might be better to use sheets of paper.
Concerining "real life"costs, Epson Premium Luster is by far the most efficient for us. We get very predictable output with that paper (using 30 meter, 44 inch rolls).
Recently, we started using the hahnemuhle fine art pearl and altough we sell these prints at a much higher price respect EPS luster we also have a much higher waste: quality issues with the paper, carton like curling, ink spreads.
Waste is an important factor to consider. Good profiles, soft-proofing, actual proofing crop will help you to cut-down on costs.
Everything else is just a matter of how much you have paid for you ink, paper and the period of machine depreciation (I remember that Michael wrote an article on this for Epson 4800, just have a look on articles on lum-landscape homepage).
Thanks Julian for your estimations!
Yes, I was aware that the printing costs vary very much, depending on several things. That's why I was asking for just personal experiences to give myself just a ballpark image of the costs.
I'm currently leaning on the HP9180. This would enable me to have 30x20cm prints as a starting point, but giving me the freedom to printing even bigger ones, for the those photos that simply scream "huge print".
I probably will hold on to this thought of buying myself a printer for a while, until I see that other people want to have my photos on their walls. That way, I can get my money back for the printer, and not only count it as one more expense in this expensive hobby of mine. But this is a whole other story.
Thanks for the replies