Another way to look at it is this:
So even if 4 IPCs is too cheap, 5 IPCs would put them into solidly useless territory. 1/2/2 for 5, or 3/3/2 for 6. It’s just not an option to move the price from 4. At all. I don’t think anyone is going to argue that tanks are too cheap, and if they do, it would surprise the hell out of me. You cannot raise their price.
Is 4 IPCs too cheap for their attributes? I don’t particularly agree with this, but let’s just go with it and see where it leads us.
How do you fix it? You can only change things with integer values. You can’t touch speed because that’s their defining feature. So, bumping up/down any one attribute, be it price, attack, defense, is all you have left, and that is massive. Seriously, Massive.
Putting their defense on 1? Yeah, okay, they are still fodder for attacks supported by air/armor, and yeah, they can still attack with artillery, but their defensive value being lowered is still a humongous change. Russia’s ability to push back against Germany is solidified hardcore by that change. I don’t have the time or willpower at the moment to really think about what all that change might imply, but my gut feeling, and first thoughts, make me think it’s too drastic of a change and would require a bunch of ripple effects all across the board that puts this discussion firmly into the not-for-this-forum territory.
That only really leaves: What if you make mechs not pair with artillery? Would they still be “too strong” then? Nope. Would they be “too weak”? Yeah, I think you’d risk putting them into cruiser territory. The ones you start with? Cool! Would you ever build new ones? Yeah, if your buy immediately matters the next turn and you had to finagle the last 2-3 IPCs around to maximum effect, but other than that? There are just too many instances where 3 art and then 3 mech inf. out of a mIC is a game-changer, or where without mech inf catching up to your art stack somewhere means your front is effectively deadlocked.
And then to the original proposition which I don’t agree with: are mechs actually too strong for 4 IPCs? They are, situationally (hi germany! :D), quite great for 4 IPCs, but I in no way feel that they are “broken” at this price. Are mechs plus a few tanks clearly the best option for Germany headed toward Moscow for something like G1-G5, depending on the game and turn of DoW? I’d say so, yeah, but then you also have guys doing the dark skies shtick so obviously there are truly viable alternatives. Then, although rare, you do get those games with German investment in the med/eastern atl due to weird shit (like a dice-failed or nearly 50/50 odds scramble on Taranto) or a Sea Lion. Mechs are also the only thing that keep UK Pac and the UK stronghold in the middle east to help out Russia a thing that works. You mess with mechs by making them weaker, and UK’s middle east/india options are shitcanned pretty hard.
Mechs would not be the first thing I would touch on if I were aiming to mess with or complain about the game.
(Speaking of YG’s houserule that mechs can drag artillery, that has been discussed elsewhere, and it literally does break the game. This is unilaterally awful for the Allies. If you want to argue about that, start a thread in the homebrew section and PM it to me–I’ll gladly shoot it the fuck down–but this thread/forum is not the place to do it.)