Choosing a bow is a very difficult task. You have to consider about 5 things all at once and even then some indecision is still present. Now, I can't say, "You should buy this one because...." I can't say that because I don't know your style and what you're playing.
I can, however, give some guide lines but still: take someone with you and try multiple bows.
Consider the material: pernambuco, brazilwood, snakewood, carbon fiber?
All of these materials factor into price which is normally the deciding factor.
For consistency, carbon fiber. For sound quality, fine pernambuco. But, the better the material, the higher the price.
Style: French or German?
Once again, what are you playing?
I've found that German bows are better for powerful, slow, dramatic pieces. French bows tend to be better for more articulated pieces that require fast moving eighth or sixteenth notes. This really isn't a factor for price, more just personal preference.
Weight: heavier or lighter?
Weight really depends on preference. I prefer a heavier bow because it just feels better.
When you go to buy a bow make sure that the dealer is reputable. You don't want to be fooled when you're buying a neccessity.
Also, ask about trial periods. Most shops will let you take home a few bows and try them out for a week or so. If your shop does offer a trial period take one made of pernambuco, carbon fiber, and brazilwood and switch it up between French and German styles.
If there's anything else I can do for you, let me know.