I`m not sayin Prod. is worthless, far fom it, but benefits different nations differently at the progressing campaign.
And the limit of research is a serious concern, especially in case of Russia: you absolutely need to start the major techs asap: Inf., Tanks, Fighters, TacBombers, Air Defense; then C&C, Inf.- Armored- and Aerial Warfare in this order.
This totals 1750 MPPs, when C&C + AD are chitted twice. Leaves only 1 major research open, which should be Ind.. In this case and during the early stage of the war it`s far mor worth than Prod., because you will mainly command cheap Korps and Armies, which don`t benefit much from Prod., because they`re already at a discount.
And even when you got some of those techs out of the way, Arty, LongRange and especially Logistics are far more important, and the second chit on Ind. Opportunity costs.
When exactly did the Prod Tech rules change?
31. of February 2017, 6.42 a.m., hehe. I can remember Bill or Hubert discussing if it was worth to implement the discount on upgrades, but did`nt come to a conclusion. It`s really not very serious is it, as it applies to both sides?
Fact is the manual is of limited value right now, and if you didn`t follow the numerous patchnotes there`s no way to keep updated.