"Putting a tax on good performers"
LOL. The smoke is literally used to cover for mistakes....
It's not always the case but for the economy of the argument I will concede on this.
The OP makes the case that, because tanks are generally (in his mind atleast) more effective than other lighter tanks/vehicles in most cases (citation needed), it makes sense to tax them the use of protective smoke due to this than the game currently does (by making the cost flat across every vehicle).
It's clearly a "better performance assumed tax" and nothing nothing else, and I 100% disagree with that notion.
I would also argue that NO, light vehicles should be "more expensive" with this due to the fact that a single, well placed shot with Katyusha/Nebel/Stuka can kill 3-4 full health squads and thus, by giving this vehicle the ability to also get out for free using smoke is more gamebreaking than, say, a PzIV getting a lucky wipe. As such, make the cost for Panzer Tactician smoke on RocketVehicles 120muni. (Obviously I do not agree with this, I am just replicating the thought process).