Making penals cheaper and keeping their stats will make then very alike to conscripts. Precisely the thing no one wants.
Conscripts and penals are early-game infantry, so they can't be buffed because that would cause a great imbalance afterwards.
The solution should be playing with their roles, making one a CQC unit (conscripts) and the other a support mid-long range unit (penals). The issue there is that in that case penal's background goes to the trash, as they should be a powerful suicide unit being always in the frontline.
Inverting roles (cons = mid range, penals = short range) would destroy grens/conscripts balance.
The worst solution is keeping both units effective only at short range, as they are now.
I personally prefer having penals like they were before. A mid range unit, but with flamethrowers for CQC and satchels to go rambo against enemy emplacements to keep their suicide-missions flavour. They should have their price increased at 300 mp or such.
Cons will keep being shit, but having penals doing damage from afar will balance the early infantry engagements.
But penals should not be suicide units, penal battalions were not suicide battalions IRL, they were simple soldiers that were given the hardests tasks. (Relic as usual went with the stupid stereotypical cliches, instead of historical research). The maximum duration for staying in a penal battalion was 3 months, and if you survived, you were given all your ranks back, and possibly even new awards.
Penal troops were armed with normal weapons, mosins, ppsh, DP-28s and stuff alike. Altho i believe they had a higher allocation of flamethrowers (Not sure about this one). (And as usual relic went with the usual stereotypical cliche that conscripts had no weapons)
In my eyes, conscripts should be long range, and penals should be mid-short range.
tl;dr - Relic likes to stereotype and cliche things