317L is only special order, so it needs to be a big job, about 2-2.5x the 304 price.
6%Mo is steep, at least 4x, maybe a little more. But these alloys are strong also so you can use less metal than with 3xx.
And these (like the duplex) really have to be made right, annealing, quenching, and cleaning are critical for corrosion resistance.
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P.E. Metallurgy, Plymouth Tube