I wrote a couple of articles in 2009 and 2010 on Ibiquity's HD radio, focusing on the AM band.
I have never heard of a $50 fee per radio for the listener. They have a hard enough time encouraging new listeners now, particularly in the AM band.
In 2009, the FCC showed 289 licensed IBOC stations on the AM band. Today, more than 3 years later, the total is 298. They have gained 9 stations in 3+ years.
At some point I hope they give up on AM IBOC. First of all, it is nothing less than a monopoly sanctioned and fueled by the government. Second, it causes an interference mess across the AM band at night.