Like so much in life what you spend will get you a cheap one or a good one. If you are going for fun and all a cheap one will work about as well as many of the old original period tang sights. If you are going to get into serious competion with a lot of elev/windage adjustments and need to take notes on the setting and have repeatability rather than frustration you will have to pay more. It is a shock to find out a sight will cost as much, or more, than your rifle!
So, which end of the scale are you thinkin' of being and we can give you some meaningful thoughts for consideration.