Canon brand Speedlites aren't cheap... but they are very good. I don't happen to own any non-Canon speedlites (I have in the past... just not any more.)
Part of what really pushed me to the Canon system was when Canon introduced their radio technology. Previously the only decent radio system that supported full E-TTL II was the PocketWizard system... but that system was very expensive (add the cost of the PocketWizards to the cost of the flash units and you're definitely not saving money). But PocketWizard had reliability issues and I found that the Canon system was rock-solid. So I made the choice to stick with all Canon units.
There are numerous cheap flashes - some of which are E-TTL compatible (which can mean a broad spectrum of compatability... many "compatible" Speedlites can't do everything the E-TTL system supports.) You'll probably notice the build quality isn't as good. The reliability may also not be as good (though some people have great luck with them.)
I've encountered people who have issues such as inconsistent brightness level between shots (even though the capacitors on the flash had time to recover and were ready for the next shot) and that would be a problem (not knowing exactly how much light you'll get when you take the next shot.)
It's not all negative... some people use 3rd party strobes, love them, and have great success using them.
So just be aware, that while you can save money... the experience may vary.
You can find a lot of advice over at Strobist (strobist.blogspot.com)