At the limit, the slice of pie pricing is completely continuous and each incremental subscriber lowers the cost for everyone. This one may be coarser grained.
Nothing inherently shady or anticompetitive about such a scheme. It also tends to arise where governments (like SEC, or like county clerk offices) have a dual mission of providing public access while offsetting costs, and need/want to outsource it to a for profit service provider.
Edit: downvoting does not change this fact either.
Also, note that you are paying to receive an electronic feed of a company's public SEC filings, which include filings detailing purchase and sale of stock by the company's employees, which are called "insiders" in this context.
The phrase "insider data" conjures images of insider trading, which relies on trading on material non-public information, and something quite different.
[1] http://online.wsj.com/articles/fast-traders-are-getting-data... (paywall, Google the title to bypass)
http://contracts.onecle.com/edgar-online/trw.svc.1998.09.11....