Not including protein powders in the protein chart is pretty stupid. Whey protein is cheaper per gram than anything else on that chart, and vegan protein powders (like soy or pea protein) are even cheaper
It depends on the country for soy. Objectively in the absence of interference, it's cheaper and still relatively complete.
But for whatever reason, a lot of Western governments like the US and Australia heavily subsidise animal proteins, so I think in those regions WPC still has a slight edge.
Then again a lot of people struggle with lactose And soy is probably cheaper than WPI.