A few years ago, $COMPANY had similar needs for a client. I ended up creating an in-house solution, which has a surprisingly close API (well, there are only so many ways to do this).

So I asked myself: if this kit existed at the time, would we have used it? I don't think so. For all specified pricing plans, the document limit is way too low for what $COMPANY or its clients do. Judging by the progression of the costs, we'd have gone in-house instead of negotiating an Enterprise plan.

If you don't want to adjust pricing, perhaps you could add a consumption based plan. The plan could have a much larger limit, but the client also pays per API call.