Most hosting companies doesn't even really want colocation anymore, it's sort a niche product.
There are some places that have jellybean colocation offers (e.g. Hetzner does - notice their normal business is jellybean servers and they run their own data centers, so it looks like a no-brainer to fit colocation into that business model), but it only covers a small portion of colocation possibilities.
But typically colocation is just one of those products where every deal is fully custom. That's just how it is. So you have to buy enough of the product to make it worth the salesman's and engineer's time, meaning at least a couple hundred dollars a month worth.
By the way, the same is true for business internet access. If you pay the cheapest price for internet (as every residential user does), you get the same basic service as everyone else. But if you're willing to spedn enough money, your ISP will negotiate with you. Though I hear it sometimes takes some prodding to get past the "residential area == ordinary residential connection" assumption (and in many cases their network may not support certain upgrades). And it's true for business transactions in general. You want five screws, grab the best match off the shelf. You want five million screws, we'll make them to your exact specifications boss. (Also related: If you owe the bank a hundred billion dollars, the bank has a problem.)