We're talking cost effectiveness.
What you get for the money you paid.
Put WC51, M3, Greyhound, M20 and 222 next to each other and you'll see one greatly standing out with what it does and for what you pay.
You realize that changes literally NOTHING? Not even the amount of PTRS shots it takes? And you still have too cost efficient vehicle.
Pair of 222s doesn't struggle nor needs a long time to kill T70, front or rear, doesn't matter, it'll be dead within next 10-15 seconds.
AEC is hardcountered by dual 222 which cost considerably less then AEC.
Only Stuart can stand up to them.
Again, 2x222 hardcounters AEC for considerably lesser cost. If you micro better then average potato, you won't even lose single 222.
Wc51 and Greyground are well known to be underpowered units for their price so comparing them to the 222 isn't fair as they should be stronger for their cost. As for M3 and m20 you could argue that these could use a small price reduction (fuel for m3, manpower for m20). So this doesn't necessarily justify a price increase to the 222 if these units have their own issues.
I do agree that the 222 should be slightly nerfed but I don't think price increase is the right way, unless you subsequently wanted to buff its armour and/or dps.
Oh yeah its sooo easy to just rush in with 222s and kill a t70 or aec without sacrificing them also. Maybe for someone who doesn't play the game or plays against players who don't know how to micro this may be the case but in most cases they will support or back away the light tank so that its more dangerous for you to continue rushing in with said 222s.
As previously pointed out the 222 has crappy armour so even if you happen to be very careful with them your gonna be spending an age to constantly repair them.