One of the things you need to do if selling your work is to be realistic about the cost to you of each print - both in terms of dollars and time.
Here's a little list of some of the costs of making a print
paper - but don't forget to add in a fair share of all the trial runs, ink blotched, bent, damaged or otherwise unsalable prints - could be that in real life you use three sheets (hell, 25 is probably more like it) for every one you sell, if you start counting from the first print made.
ink - see above re trial runs though, and what about nozzle cleaning - with Epson pigment printers, that's a huge cost that you must factor in - there are some useful references on the net to ink used per print produced that take into consideration nozzle cleaning - but if you print intermittently - better double the cost to allow for more nozzle cleaning.
printer wear - printers don't last forever - if you are good enough to sell your work, you are doing a lot of printing and should realistically amortize the cost of the printer over two years. In the mean time at least two newer sexier and perhaps better printers will come out. Within a year of the 4000 coming out, along came the 4800 which apart from having epson's black and white print driver and less bronzing on gloss papers and a wider gamut, also removed the second black container making it a hell of a lot more expensive and difficult to switch from matte to glossy and back.
Containment - if you sell more than a few prints, you soon run out of print boxes. For myself I have to figure in the cost of the mylar art bags - roughly $1 each, depending on size. I have litterally spent thousands in the last two years on acid free foam core. I get 5 13X19 from one sheet, 2 17X22 but only 1 24X24 from each sheet.
Shipping: if you mail, you have the ups or post office cost but don't forget the packaging cost - for a mailing tube if rolled, plus cost of a protective sheet you roll up with the print so the image doesn't rub - I used a roll of vellum - handy but probably not the cheapest. When shipping flat, the only way I have found to reasonably guarantee safe arrival of a print is to put it in the mylar bag and tape that to a sheet of 1/8 inch hardboard (masonite).
Returns - better factor in the cost of some images being lost or damaged in transit so you have to replace the whole package. Even when not shipping, if the customer drops a print on its corner while standing talking to you, you are likely going to swallow the cost of the replacement.
Time - you might be tempted not to charge for your time, but that's only because you are selling one print - get lucky and have 50 sales and I bet you start to feel differently about how much your time is worth.
Computers - this is a bit more controversial as you know damn well you would have had the computer anyway, but you might have bought a new one because of the business being done, a bigger, faster one with more hard drives so you may want to take that into consideration.
Artistic Worth - this is a topic for a whole other discussion so we'll just say for now that opens a whole can of worms.
And I'm sure I have forgotten other factors and deliberately left out several - the cost of camera gear, travel, burned dvd's etc.
Does make you think though.