So same hummus, same factory, different labels, different price.
When I was a student in the early 80s, lots of us did summer work at the local Mr. Kipling cake factory. It was a revelation to me that they also packed cakes for many shops' 'own' brands, and the price difference between the most expensive and the cheapest, for the same cake was 11p!
Also hygiene was appalling - e.g. workers going to the loo and not washing hands, cloths being used to wipe the floor, then the inside of a mixing vat - so I wonder if poor hygiene is at the root of this outbreak?