Only Cerebras is doing wafer-scale. It seems to be working for them but no one is copying them. The minimum unit (one wafer) costs millions and it's not clear how good their multi-wafer scaling is.
A 300mm wafer on a recent process node (TSMC N3) is estimated to be around $20k at quantity[1]. I don't know what kind of testing and crazy packaging processes would cost for a wafer-scale chip, but I can't imagine it would put the price anywhere near the millions.