^^^ (sloped armor)
How much of the delay on making sloped armor more of a norm was related to overall cost of production? Do you need to nclude considering the type of steel itself, combined with assembly: riveting vs casting vs welding, and trained labor for those specific assembly methods?
Also while the advantages to sloped armor was understood prior to WW2, the big disadvantage to using it was lack of interior space. Large guns, ammo storage, radios and crew require a certain amount of workable space to function effectively. Adding sloped plate armor to those working parameters usually result in an over sized vehicle. The T34, while a breakthrough design in many respects, would have been viewed as unacceptable in the West.
ric350
From the analysis of interwar vehicles with sloped armor, this doesn't appear to have involved any additional cost or difficulty and if anything could simplify construction by reducing the number of plates. American experience with T4 Combat Car's sloped plate would also indicate that, contrary to my initial assumption, high levels of sloping were still valid from a weight efficiency standpoint even against bullets. It is also worth noting that given that the armor on the turret, sides and rear of the vehicle are pretty much dictated by other geometrical factors, the only place where a debate really occurs is the front hull.
For the front hull, there was a debate between single sloped plate and a stepped layout (with or without an angled driver's visor plate). The latter, more common layout seems to have been dictated both by the design of observation devices, the installation requirements of certain bow machineguns, and finally an idea of just conforming to the location and shape of the driver without studying the exact optimal layout to accomodate a single sloped plate.
The question of internal volume is not very valid because even on sloped armor tanks, the volume was decided from the start, the sloped armor is not eating into a space that people wanted to use. Ergo T-34 had the space it was because the engineers thought this space was sufficient, not because it had sloped armor.
I would add the rare case of the British Crusader where officers reported that "sloped plates should be used less, like on the hull nose". In this specific context, this was most likely PTSD caused by engineers which overestimated the actual ballistic performance of the sloped plates and made them thinner than needed as a result. However, this is a problem of armour testing and design to an armor basis rather than a fundamental issue of sloped plates (in comparison, the French were far more rigorous with the thickness of sloped plates so wouldn't have had this issue). In addition, once the problem was identified it was suggested to simply rework the thicknesses to get the same basis (of 50mm).
