Wtf? It's a damn 85mm. It can actually penetrate something. It also has more survivability than a 76 because of its improved armor(health?). And thanks to those two things, an 85 can reliably slug it out with other tanks while a 76 has no hope of doing so. The T34/85 is an actual useful medium tank, equivalent to a Cromwell or an Easy Eight. And the 85 does not need to flank to win its tank battles (obviously unless it's vs German heavies, in case which case EVERY Allied tank needs to flank to get any fighting chance whatsoever)
"cost efficient"? T34/76? Really? It cant pen shit, it cant kill anything unless it goes on a suicide flanking run, and (like the others have said) it actually has worse anti-inf than an 85. Hell the T34/76 is even more useless now because of the T70, formerly a frail infantry-wipe-machine, now turned into a normal light tank. Which means the T70 is now pretty much (an only slightly worse) T34/76 that you can get way earlier (and cheaper).
I can't tell you how many times I've had 3-6 T34/76's go on one of these "suicide rushes" and take out Tigers, King Tigers, or even a small group of panthers with minimal losses. The other week I lost 2 Panthers (one vet 2, one Vet 1) to only four T34/76's due to me being surprised and the other player's outstanding micro. The sacrificial lamb would lead the attack and get behind my tanks preventing them from backing up with the others went to both sides of the panthers. I didn't even destroy a single one. One was an inch from death and another was severely damaged but both were able to retreat and repair.
I'm sure someone has a replay of this happening. It's happened to me quite a few times with minimal losses to Soviets.
It CAN go wrong. If they bumrush i this fashion in an area where your tanks are plus AT guns behind the tanks they're gonna have a very bad time. Or if the axis player sees it coming soon enough and kites the T34's in reverse.