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It depends a lot on how you do it - no matter how much you pour into a vanity press, very little will come out. Are you thinking of doing a book of poems? If so, how long? If it's normal length (at least 100 pages), querying publishers could work well if you want to go the traditional route. That costs nothing but time and postage - you should never pay either an agent or a publisher to look at your work. Though you may want to pay an editor to go over it so you're putting your best foot forward.
If it's shorter and/or you'd prefer to do it yourself, cost depends on format. In Canada and the US, ISBNs are free when you register, so that's something. Then you'll want, at the very least, a copyeditor and an artist to do the cover. Copyediting will typically start at $30/hour and go up from there, and a lot of the editors I know can do maybe 10 pages an hour. Artists will vary more widely, but typically budget at least $250 for the art.
If it's short, you might want to release it as a chapbook, which can be cool as an art piece in and of itself but mostly means that you'll want it to look more handmade, so spending more on paper and then doing the binding yourself is something lots of people do, then distributing to local booksellers. That's probably going to be somewhat low return, but has a very cool end product.
Electronic release is excellent, and Amazon makes it pretty easy. You can theoretically do the layout yourself, but paying someone else to do it might produce a more polished final product, based on your skills. Probably $400 for formatting. You can also make it available for print-on-demand this way, though add another $100 probably if you're getting the same designer to do it.
If you want to get it published at a printer and then distribute it, cost will depend on the size of the book and the size of the print run, and will vary wildly - expect nothing less than $500 or so.
So bare minimum cost of nothing if you shop it out. Bare minimum of $250 + $30/10 pages doing it yourself, and very easy to spend north of $1500.