We just picked up our new MH two weeks ago this Friday. I wasn't really ready to make the move. Another 8 months to a year was more in our time frame. One of the reasons we moved on this rig was the increase in build costs due to the reason discussed in the OP.
I'm in the distribution business and many suppliers costs are increasing because of this. Customers steel prices are going up too. So yes, it's getting passed on. Not all manufactures are running huge profit margins. Especially if they're doing work for the big three.
That being said, I was told that as new 2019 rigs coming from the manufactures they were going to see a 6% and up increase in cost. On our MH it would have been around $13,000 more if we waited. Also the interest rates are going up too. So we bit the bullet and bought now. I believe what I was told as It's confirmed in my industry.