I suppose “roadbase” varies to the local. Around here it's a combo of crushed rock, sand, dirt and sometimes a little lime is added. Spreading about 3-4 inches down the crown will be near a 100 ton for 3000' and it runs $9.50 here. That makes a fine drive by itself, but topping with a crushed rock will look better and double the cost. It's almost like painting in that the base will mirror the surface it's put over. The crushed rock then will kind of seek out the bad spots as it's driven on so the combo of the two works best.
You don't get that much traffic on a driveway but it's sort of a point of pride to do it right.

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89 300E
79 240D
72 Westy
63 Bug sunroof
85 Jeep CJ7
86 Chevy 6.2l diesel PU

"The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."
Marcus Aurelius