Alright, so, say I send to a printer. I'm going to use Ka-Blam.com as reference as they're a fairly well-known print on demand service with quality prints. They specialize in comics, which is a bonus over services like LuLu, which tends to print really terrible-quality comics.
If I want to sell 100 copies of my comic, I'm going to have to purchase 100 copies. I can print a 200 page book for around $5, so in order to make the full run, I'm going to have to pay $500 out of pocket. In order to cover my cost, I'd have to charge $10 per comic, $15 to make a profit if I intend to make a second run. That's in black and white WITH a Ka-Blam ad in the interior cover (which cuts cost by about, eh $0.20 per book).
Oh wait, if I print it myself, I have to distribute it myself as well. Most stores won't take a book that's printed through a print-on-demand service because they have to actually buy the book. Their other publishers compensate them for books not sold, whereas they cannot do that with a print-on-demand book. I have to cover costs of shipping, or if I have a distributor, pay them to do it for me. I also have to have several copies on hand and spend the money in gas to get to conventions to peddle my book. All in all, this could force the price of the book up to $20 or $25, and I may still not be making profit.
If I went with a publisher like FurPlanet, if my calculations are correct, a similar book would cost around $17 from them, which while expensive is still more appealing to buyers. There was no amount of money that came out of my pocket to have these books printed, and they distribute both online and at conventions for me. They would pay quarterly, and I could negotiate with them to set the profit amount for the books. They print several copies to tote to cons and print everything else on demand for their online sales, which means that they can distribute a more exact amount while spending less on a bunch of wasted copies.
In the end, I could potentially make more money going to a small publisher than trying to print on my own, while providing a product with a price that more buyers are willing to spend (which equals more sales, which equals more money to me).
And, just FYI, any printing company is going to charge enough to profit on their prints of your work. That's the same as a publisher who prints your book for you taking the money for supplies and profit for their work out of the sales.