Couple points:
1. FTP players increase the overall population and help avoid the dead game feels dead problem.
2. FTP can and do spend cash in the cartel market.
3. MMO prices have most defiantly changed over time. Most of the MMOs when I started playing them were 9.99 a month. (Im not going to go back and reference the days of paying 5 bucks an hour etc, yes Im old)