60-80 is about as high as you can go. It's probably actually a waste to pin that much honestly. 6K followers is not enough for 1K clickthroughs. If you had a 6K audience on adwords you wouldn't get that.
It's more about how many followers are seeing your stuff in their feed.
Best way to scale up is make more accounts and follow targeted people. You will get 6-12% following back, and they will see your stuff chronologically when you pin.
You can follow a certain amount per IP, regardless of what account you are on. Get a proxy or 2 and run 2-3 accounts on each IP using whatever automation you prefer. iMacros is a good choice.
Pin random popular bullshit, possibly also using iMacros or your software of choice. This is just to dilute your money pins, which you should pin at peak times.
It's all about scale.