Refractometers

[WhipCityBeeMan]

I am considering buying a refractometer and as I look at them online there is a wide range of prices.  Some are 20 bucks all the way up to several hundred.  Ebay has a bunch listed that I assume have varying degrees of quality/accuracy.  Does anyone have one they recommend and how expensive was it?  What is reasonable for a hobbyist to pay for one?  How many of you find it to be necessary/useful? 

Any info would be helpful.