You also need an ISBN and if you're in the US those are ludicrously priced: $125 for one, $250 for a block of 10, $575 in a block of 100. Since Smash only takes a very small percent of the cover price, about 10%, you have to sell a pretty significant number of books before you break even on the ISBN. If you're in Canada disregard because they're free. Lucky you.
My cocktail napkin math:
So take 10% of your cover price, then divide $25 by that number. If you have ten titles and you buy a block of ten, that's the number of copies you need to sell to break even over going with Smashwords.
The math of a single ISBN is dismal. $125/.29= 431. You would need to sell 431 copies on iTunes at $2.99 before going direct made you more money than Smashwords.
Buying a block of 10, you need to sell some combination of 862 copies on 1 to 10 titles on iTunes at $2.99 to break even. That could be one book that sold 862 copies or 10 that sold 86. Given how poor sales are on iTunes compared to Amazon or B&N, that's an awful lot of product to move.
TLDR If your overall sales are below 1000 copies per title, Smashwords will most likely net you more money.