The IQ2 power meter is listed at €129 for one foot.

https://www.iqsquare.com/

They aren't shipping yet, but assuming they get their current issues resolved, they could be shipping by mid-summer.

I think there was a crank strain gauge kit that also came out cheap initially, but has now become a more commercial product, and more expensive. Was that Stages?

But, no doubt, more will enter the market, especially if production can be simplified (which is what IQ2 was trying to do).

XPedo had done some initial development on a power meter, but seems to have not released it yet.