I dunno if I can be much help, since I've paid at least $110 for every servo I've bought!.
I would say:
1/10th scale 2 wheel drive (RC10GT, Rustler, Jato):
80-110 oz/in
1/10th scale mini-truggy 4wd (crt.5, ls10, DST):
80-120 oz/in
1/8th Buggy 4wd:
100-175 oz/in
1/8th Truggy - Muggy:
130-200+ oz/in
E-Maxx - Revo - Savage - LST (Single servo setups):
120-200+ oz/in
The only thing I would consider "overkill" is the Hitec HS7955TG. That I'd say is mainly for large crawler use.