Unit costs for HTPB and PBAN seem unreasonably high.

[bfrobin446]

Stock SolidFuel costs 0.6 Funds per stock unit. RealFuels scales that cost by the same factor that it applies to the density of the stock resource, making SolidFuel cost 0.14238 per liter.

But if we want to make a motor use a specific type of solid fuel, HTPB costs 1.8585 per liter, and PBAN costs 1.593 per liter. We could divide both of those costs by 10 and and still be slightly more expensive than generic SolidFuel.