You may be right. There was apparently some pretty sweet deals over the years. In 2010 list on the FTM-350R was $780, HRO had it priced at $570 and then $110 in rebates. So the final was $459.95 + tax. The FGPS-1 was $74.95 + tax.
Haven't been able to find my receipt, but looks like when I got the updated radio, the FTM-350AR, it was approximately $540 after rebates. So I was around $620 or so with the FGPS-1. That's about $50 less than the FTM-400 is going for right about now.