Other than Conscripts, who are 257mp + 50mu. Volks are slightly cheaper, but are worse. Rifles and Sections do cost more when fully upgraded though, of course.
Not that I'm saying that VSL Grens should beat all other mainlines, but they obviously aren't the cheapest infantry.
Agreed. For one the upgrade isn't cheap and grenadiers are not the cheapest squads to reinforce. It is being argued heavily that lmg42 grens are still the most viable choice of upgrades. I think VSL grens being able to place sandbags might be a good option for them to help them maintain that 'staying power' that they need as a 5 man mainline squad. Otherwise why wait for 2 CP to upgrade to VSL when you can just reach BP1 and use LMG42s which are better and you can even use them sooner?
I mean personally what I like about German Infantry Doctrine is the upgrade for Panzergren and using them alongside Grens with their smoke and mark target, but otherwise I think the doctrine is now lacking and a lot of its abilities are better off chosen from other commanders which give you more. The point of the German Infantry Doctrine (IMO) is to have more staying power with your mainlines and providing your infantry with support they need to do it