This is a further clarification taken from Luminious Landscape. Maybe
you already read it:

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       The Black Cartridge Nightmare

When the K3 printers were announced, and particularly with reference to
the 4800, it was said by Epson that swapping the Photo Black and the
Matte Black cartridges would be straightforward and wouldn't waste much
ink. We'll, that's turned out not to be the case. In fact I find it to
be the most annoying aspect of owning a 4800, and is almost enough
reason to make the printer's other advances seem less than worthwhile.
Here's what this is all about.

The 4000 was a 7 ink printer that had 8 ink slots. This allowed the
/Photo Black/ cartridge (glossy papers) and the /Matte Black/ cartridge
(matte and fine art papers) to be loaded simultaneously, and for the
printer driver to use the one needed based on the paper chosen. Nice.
With the Photo series printers, including the 2200 and now the 2400,
swapping cartridges isn't a real issue since the ink lines are very
short, and the amount of ink wasted is small – maybe $10 worth at most.

On the larger 7000 and 9000 series printers swapping was required, but
most of the customers that used these large printers found that doing so
was a very expensive proposition – more than $100 worth of inks were
flushed into the holding tank each time just the one black cartridge was
swapped. Consequently studios and labs typically devoted one printer to
just one type of ink and used a second printer for the other.

But with the introduction of the 4000 printer in 2004 we had an ideal
situation, and the typical purchaser of these printers, small to medium
size studios, fine art printers, pre-press houses, small labs, ad
agencies etc, didn't have to waste money and space with a second
printer. It was a do-it-all device, produced great image quality, was
rugged and reliable, offered versatile paper handling, and was an
all-around terrific printer for the photographer or artist who needed
different types of output, depending on the client and a particular
job's needs.

But then with the 4800 and K3 inks Epson has added a /Light-Light Black/
cartridge, taking up the slot that the second black cartridge on the
4000 occupied. If what Epson had intimated, that changing cartridges
would be of moderate ink cost and effort, the exchange might have been
worthwhile, but I feel that it wasn't.

Yes, the new three black ink design does provide some benefits.
Monochrome images are superior and there is an overall improvement in
tonalities. But, the overall cost of this is very high.

Firstly, the act of changing cartridges can take from 10-30 minutes.
Part of the problem is that manual intervention is needed every few
minutes. One has to stand by the computer the whole time waiting for the
top-panel LCD to inform you to raise and lower the two levers next to
each side's cartridge grouping. This can be required anywhere, in my
experience, from 6 -12 times. (/I'm thinking of suing Epson for
physiotherapy costs due to carpal tunnel syndrome/). On a more serious
note, it means that since the printer often sits for periods of time
without making noise, and then starts and stops as it pumps ink in and
out of the lines, you can't just sit at your desk and listen for when
manual attention is needed. You actually have to stand there, sometime
for close to half an hour.

But the kicker is that ALL of the inks are depleted every time you
change the black cartridge. I estimate that about 10% of the printer's
total ink capacity is lost each time the black cartridge is exchanged.
This means about a US $75 hit. Not a good thing!

Users should also note that (on the Mac at least) one needs to delete
and then reinstall the printer from the Preferences utility, otherwise
the driver refuses to understand that the ink has been changed and that
you can now print on a different selection of papers. This seems to be
simply a matter of poor programming on Epson's part, since the printer
and the driver talk to each other about other topics, so why not this one?

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Like I said if you want to stay with Epson look at a 3800 but you are
limited to 17" wide. I would look at the Canon IPF6100.