“A new Mode C txpdr can be bought for under £1000.”
More importantly a second hand one is £250 ish. This is one of the reasons getting the ban on fitting Mode C removed was important. As a direct result of this the number of mode c transponders on the LAA fleet has risen to current levels.
“Look at the USA, many "homebuilt" aeroplanes have them.”
“many” UK home builts have them, 30% is 1100 + (total LAA fleet 4300 ish). If you introduce the US rules and remove the Euro/CAA restrictions, transponder usage on home builts would increase by 50% in my opinion. The empty weight nonsense, for example, has no equivalent in the USA so 5000 UK aircraft can now fit them in one stroke of the pen.
Rod1