Regfee and $0 are different when is I use the terms in the appraisal section. $0 mean true no value. Its squgly, return it if you can, trademark problems
Regfee can mean several things(to me), that the name most likely wont be sold for any real money but has some logic behind it. That it can be the start of a mini site and get a few click down the road, may get a bid(s) on a forum or ebay starting at a dollar and not at the end of its reg year, could get stray hits and clicks on parking.
In other words think of regfee as a single digit appraisal value $x