Not much, yet.

$20 on VII (twice...so $40)
$30 for VIII
$20 (approximately) for IX.

$90 - not bad, I guess. Would have been less if my first copy of VII didn't get a terrible scratch on disk 1 and not let me finish playing. -_-

Not to mention the system I bought for the sole purpose of playing the games. The rest have been roms and stuff, but I'll probably get my own copies of them one of these days.