Although what you find frequently is that SmallQualityCorp was started by BigCorp at arms length with a view to bringing them under the umbrella once they have traction.

"Sports nutrition" (the "what the hell do we do with all this cheese making byproduct industry") is rife with this - there are only two suppliers, and many, many brands and offshoots. It happens in retail, too - you see a single entity pushing multiple seemingly independent brands to target different market segments.

Then how is MyProtein so much cheaper than like everyone else?

Volume over per-sale margin. It's the exact same stuff from the same suppliers as you'd get buying a premium brand like Sci-MX etc.

See: Snapple