Although it is quite difficult to give a straightforward answer to this question, it could easily be said that a reliable model will cost you at least 40 dollars or more. In fact, depending on the brand, the price of a unit can actually vary quite a lot.
Nevertheless, the models designed and produced by top-notch brands are known for being a bit more expensive than their similar counterparts produced by unknown manufacturers. Still, if you want a good pair of boots, it might be a good idea to check for additional features such as reliability, weight, etc.