Does any one know if there is a car thats similar and much eisier to find buts also on a bugetI can't comment on price or the specific 'GC8' chassis but here's how current numbers of US based Impreza 2.5RS vehicles on the road are looking over the past 6 years. Coupe and Sedan are grouped. Approx. 5,854 2.5RS' remained in operation in 2020 (down about 10% per year since 2015)
You can extrapolate this out to get an idea of what it will be like in 10 years however I imagine the numbers will plateau and begin to level off as people drive them less/"collect".