I've been a LONG time member of TD Ameritrade (e.g., joined back when it first became just "Ameritrade"). They classify me as an "APEX Member," which means I pay only 8.00 per trade on any stock from the OTCs to the NYSE. I like it.
You are 100% right and I was wrong they do charge a higher percentage on penny stocks. Since I don't sell very often and didn't even pay attention to the cost when I bought. Oh well live and learn.