Captured shop ladder
Grey x1.5 costs $25K, Blue x2 costs $100K, Purple x3 costs $500K, and Red x4 costs $5M in the September 8 screenshot field report.
Compare against treadmill
A multiplier becomes valuable when you train often enough to recover its cash cost. The underlying Speed gain depends on your treadmill level; Level 3 was observed at +25 per step.