Since you haven't gotten a response from an expert or a local yet, I will provide my limited knowledge.
Probably the bottom of the value list is "fill dirt" - this can be practically anything (clay, subsoil, rocks, sand, in mixes) not composed of excessive organics (which would rot and decrease in volume, and hence cause settling) or toxic materials.
Aggregates (sand, gravel) have a higher value than fill, although if the sizes are mixed up (which I think they almost always would be), a commercial operation would be required to sort by size and maximize value.
Topsoil is likely to be your highest value excavated material, which can be separated pretty easy since it's on top. The fewer the rocks, the more it's worth. "Shredded Topsoil," which has had all the rocks mechanically removed, can be (to me, who get his topsoil for the cost of having a dozer set it aside during driveway, barn, or pond construction) ridiculously expensive.
Hopefully someone near your neck of the woods can provide info on prevailing local prices.

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