I got a quote from a well-known trade-in company that I've used in the past.
Their online quote for my old Canon HV20 HDV camcorder was $420.

My HV was still in mint condition, absolutely no wear/scratches on the outside.
However, I have used it quite extensivesly. I have recorded a little over
212 HDV tapes on it in the last year. That's 212+ hours of recording,
plus another 212 hours of playing back(transfer to PC)... could be a little more,
since I kept all the HDV files on two 1TB drives and both are almost full.

Is $420 too low or too high? Will I get more money by selling it on Ebay?

212 tapes? You should buy another one and donate both to Salvation Army. That said, why ask, put it on Ebay with your limit and you will never have to wonder the what-ifs.