not at all, the $15 is for constant bugfixes, updates, customer service, content additions, etc.

All that keeps you interested in the game, so if you end up playing this game for 6 months, you've spent what, $135 and you havent bought any other games since you're playing this. So lets do some math:

one new game a month for six months:
$360

Playing SWTOR for six months:
$135

financially speaking, im saving money here.

yeah i know me and a friend both took a break from wow for a while, and in that 2-3 months my friend bought at least 5 new games..finally decided to just play wow
and dunno why but to me running heroics and stuff over and over is fun. trying to keep all the retards standing in shit alive is always a challenge. and there is always the occasional raid and some pvp thrown in there.
if you play on a console its basically playing a shooter with others. or playing a game by yourself