Say what you will about traditional publishing, but one great thing about it is that it is not very cost prohibitive. You might incur some postage sending your manuscript around or if you choose to pay an editor before pursuing publication, but agents don’t charge you until they get commission for selling your book, and publishers pay you.
Self-publishing similarly doesn’t have to be hugely cost-prohibitive, but there are a lot of tasks involved in self-publishing, such as generating a cover, editing, copyediting, formatting, self-promotion, that you’re either going to have to spend the time to do yourself or pay someone to do for you.
Depending on how much time you have to spend and your level of expertise, you may end up spending a thousand dollars or two to effectively self-publish. Can you afford that?
–Nathan Bransford on investment.