Australia

The IGA shops are small businesses, there might be a few owners who are large enough, with multiple stores to call themselves medium size, but the vast majority are owner-operators.

The large conglomerate your referring to is called Metcash, they're the primary wholesaler to IGAs but also wholesale to other shops. They also own the IGA brand in Australia at least, i don't know if theres a North American connection with the IGA brand up there.

I wouldn't assume they pay a better wage, thats almost certainly a store owners decision, which means it'll vary store by store. Maybe Metcash might give 'guidance' but they don't have direct control like Coles, Woolies, Aldi, Costco.

So, when you buy IGA more of the profits are remaining local with the owners of that store.

If i remember right Metcash' assets are through product sales and brand ownership. This is also why Metcash will likely never be able to conpete properly with Coles, Woolies, Aldi, and Costco because all of those companies have the land and buildings their stores are situated on positively affecting their borrowing capacity, Metcash doesn't have that therefore fundraising for expansion, or technology upgrades is more difficult.

That extra layer of (internal but not internal) wholesaler sales i believe is the reason why IGAs are slightly more expensive. But even then it depends on the type of IGA we're talking about, there are some really fancy ones and some not so fancy ones.

I suppose everything i just wrote is based off knowledge over 10 years old now, but i think its largely still true.