Correct, which is why they agglomerated in the first place. Sectors where you see lots of agglomeration are ones where there are significant advantages to agglomeration.
And yeah, it’s hard to do once, but obviously it’s dramatically harder to do after someone has already done it.
Its interesting how the benefits seem to be dependent on market context. Go to the ralphs, its big potato no doubt. Go to the farmers market and people are there arguably to avoid big potato and big anything else for that matter.
However even in this case customers, or Big Potato buyers, can simply ally and create a new supplier where they are shareholders.