The ring clamp came with my turntable so I didn't have to make the decision. I'll repeat some thoughts I wrote on an earlier thread:
Soundwise, it seems to tighten up the soundstage, fix the images a little more firmly. Certainly made a difference, better in my opinion. Functionally, it's an elegant alternative to the complexity of having a vacuum pump, perhaps a better solution if your record is warped. It also adds to the platter's rotating mass -- a good thing.
So far as whether it is worth the price, you have to decide if the difference in sound is what you like. If you do like it, you decide how much you want to pay for it. Heaven knows, we have lots of expensive equipment and tweaks in our hobby. Lots of us pay more than $500 for less improvement in sound just upgrading cables.