Of all the sheet products I can think of with reasonable structural value and moisture stability used in typical basement areas, plywood or OSB (waferboard) come to mind. Foam products, gypsum products, hardboard products, or other building materials available in sheets, offer little or no structural value. It's plywood or OSB (cheaper) that take the prize. Sorry to say that prices are up across the board on building products, but they will come down substantially, in my view, when the supply situation adjusts to normal production levels. I recall other times in our economy when prices dropped like a rock, but yes, this time the situation is somewhat different because of lock-downs. Most commodity plywood sold in the USA is manufactured domestically and not subject to offshore whims and container issues.
Other wood alternatives are lower grade 1 x 6 or 1 x 8 pine boards...my first layout had them exclusively with no issue at 24" OC. This inflation thing is a real problem, but I'm waiting it out to buy my preference...
It seems in most cases on the forum, contributors express their good will views for a reason, and I believe most of us have benefited by the wide variety of comments and opinions. I recall being a "newbie" here several years ago and I credit this forum for the majority of my knowledge in building my initial layout, especially, and even more so now on my second layout..
