Stages Power Meter Ultegra 6800

I’m interested in buying the Stages Ultegra 6800 for my Trek Speed Concept and currently the crank arm length is 170mm. I’d like to change to 165mm and was wondering if anyone knew what the cost would be to change out the crank set to 165mm in addition to the power meter itself? I have Ultegra components now.

Thanks

Depends on if / where you can find the crank. I just bought a 170 6800 crank on Chainlove for $219. DUnno if they had 165 or not.