M3 pulls its weight though because it's a highly effective shock unit in the early game. The capability of chasing down squads on retreat makes the unit worth its cost.
Kübelwagen isn't outright terrible, but it's certainly underperforming for its cost. Usually people lose it after a few minutes of ninja capping with it, at which point they regret not getting a volksgrenadier squad for only 40mp more.
But with M3, you have to invest in fuel plus a flame engineer squad (170MP + 60 munitions) or 300MP penals. Also, Kubel can cap and constantly harass the map and cut offs especially in 1 v 1s. Kubel got a nice armor buff few patches ago too.