In my industry, one of my biggest sellers has been on backorder since 3/10/21. I have other brands/sizes, but at a more expensive price. Another high volume item went on backorder 5/28/21. I had to grab a couple of skids of the next size up to sell. The company is taking no new orders on that whole product line currently in the short term, period. No new orders until they can get some kind of stability in their supply chains. Most of the vendors are on allocation based on past usage. I tried to order some specialty item yesterday. I couldn't get it because I hadn't bought any this year.
The point is, when you see something in stock/at a certain price, that item might have been on the shelf for some time. When the company has to reorder it, they might have trouble getting any more and the price will increase.