Not sure which size nitro touring uses, so I can't comment on that.

The two cheap servos that really impressed me for the price are:
The JX PDI-4409MG as a LP servo for 1:10 offroad. It's a bit on the weaker side and not the fastest, but there's not really anything that comes close at that price and even quite a bit above. 9kg at 0.11s (though the time-spec is really, really generous) are pretty usable for $15.
The JX PDI-6113MG as a standard size budget coreless servo. Definitely very usable as a throttle servo in a 8th scale buggy, about 14kg at 0.10s for $25 and it's coreless nature means it's a lot more responsive than a standard brushed servo.
If you want to spend a little more, PowerHD has some great servos period with more budget oriented (but definitely not cheap) options that are still very good. But they managed to build a brand so they aren't as cheap as they used to be.