I just got one of the cheaper tensiometers. I believe it is a knockoff of the Park tool. I had no expectations of it giving absolute values, but just wanted it for baseline even tension as one approaches final truing. I found it quite useful for only $25 and a bit of peace of mind is instilled in the final job. I checked one set of wheels I had done previously, and found a couple of spokes either looser or tighter by a bit and corrected.
I thought that while I did things, why not go for evenness.

I am not real confident in my ear for plucking. Just now I have some newly laced up Weinmanns that I did just before getting the meter. I’m sure they would have ridden fine, but I redid them. Not much change, but I got the evenness a bit more consistent. I also liked it for final truing to see whether to tighten one side or loosen the other for adjustments. Peace of mind I think is nice, especially with the low cost of the tool.