One should never accept a speeding fine for 1 mile over the limit.
Police radar (all manufacturers) can only be accurately certified to plus or minus 1 mph and that only applies with recent calibration.
And you can add officer's knowledge/familiarity with the equipment on top of that argument.

 

Most of those small communities around here that do (or at least did) that did not report the ticket to the BMV and had fines in the $15 to $20 range. If you just paid it out, there were no court costs. Taking it out of mayor's court (where they would find you guilty no matter how good of an attorney you were or had) involved sending it to county court where the procedures were more complex and time consuming. You had to figure on two days of court time plus a higher fine if you were found guilty plus court costs. Of course, if you won, you paid nothing except possibly the attorney you hired. I used to do it because I could handle my own case and deal with the city prosecutor's attempts to confuse the issues. For the average person, unless he was a stubborn SOB like me, it was not practical.

I agree with you about the legality of the thing. The legislature did pass laws limiting the ability of some of these small towns to issue tickets on expressways and state roads, but the home rule in the State Constitution limited what it could do beyond that.