There is at least $150 off many Pioneer power meters on Shimano cranks at Power Meter City in the USA, covering Ultegra R8000, Dura-Ace R9000 and R9100. It’s not available in every single crank length but there IS a good choice.
There are single-sided and dual options to choose from with the cheapest Ultegra, single-sided starting now at £379.99 and the cheapest dual upgrade kit at $599.
There are slightly cheaper single-sided STAGES close-out option at $349 on a R6800 and a 4iiii option at $329 (on 105).
More Info> powermetercity.com
UK Links: here