I'm not aware of of any aircraft costing less than the 8 figures equipped with FBW. It's a LOT of added complexity/cost for very little gain in anything that isn't either dynamically unstable (e.g. modern military aircraft) or so large that the flight controls can't be comfortably operated by hand, and is rare even in the bizjet and smaller airliner market.
On all small aircraft (and some larger older ones, DC-3s for instance), muscle is the only thing that moves the control surfaces. They're very well designed and counterweighted so that the required effort is quite minimal.
In the US an ultralight has to be under 254 pounds and does not require any training or licensing to fly. In most other countries an ultralight is more like the sport class in the US.
At 254 pounds you want light and simple. FBW requires actuators. And controllers. And sensors. And power. And then you have to double up everything for redundancy. You would easily eat up 50 lbs or more making a reliable FBW system and it would cost 3-4x what the entire aircraft cost.
Even with normal light aircraft a FBW system is both unneeded and overly complex. Cables and pulleys are extremely reliable. They are inspected every year (along with the engine and various other pieces of the aircraft).
