How much you should spend on bottles depends on how concerned you are about using used ones or ones that are plastic. Bottles made my list of things that some people will not use used.
If you are concerned about storing and feeding in plastic, than you many want to save some extra money to invest in glass.
If you are not however, this is usually a pretty easy item to find used for next to nothing.
We purchased and used quite a few gerber bottles. They are plastic, but BPA free and super cheap for those days we forgot to pack nipples and need to stop at meijer on the way to daycare.