They wouldn't on purpose but I can tell you from experience that what happens in practice is that you don't re-quote everything or instantly change your quoted pricing based on a small fluctuations in inputs. So most companies will eat a couple percent (gross) margin here and there. So when an input cost rises margins my go to X-1, and then X-2 as it it rises more, then someone notices and changes quoted pricing to say Y+1, 2 or 3 depending on whether you're trying to get ahead of future hikes, how bad you're being squeezed, how bad you want more work, etc. But no matter what the "area under the curve" of all this change is almost always going to be negative. Sure, there's the occasional winner but in total the entire industry and economy loses.