Yes, tone wood is expensive - it has to be the best cuts from the best trees, prepared properly and aged as well.
Other than spruce you can look at cedar; western red cedar can be good and there are a couple of other varieties that might be useable, I think. Different kinds of fir and pine have been used too, but I don't know that you'll find any these days that is what you want; you could look into things like salvaged wood from old structures and the guys who pull giant old logs out of lakes and whatnot, but you're in uncharted territory and getting pretty far from starting on a bass.
