The SFC version of NGT in particular? No, it's not significantly cheaper.
I don't think the FC versions are much cheaper either. III is getting to be expensive on NES, but the FC version is also increasing in value, due to the less crazy difficulty.
If you mean SFC games in general, RPGs and puzzle games tend to be cheap, but more action-oriented genres (platform, beat-em-up and shooter) are still usually expensive for the better games.