Have you ever considered offering a lower cost licensing option?
Maybe a single platform license offered either in one product or multiple products licenses.
For me personally, I'm looking at around $1200 to consider this for applications I develop, and I'm only interested in one OS.
At $1200 I have to do a ton of prototyping to ensure the library meets any current and future needs.
If it doesn't meet enough of my needs, the cost of developing a custom library or finding and modifying a commerciallly compatible open source library start looking pretty good.
I'm sorry if this comes off as complaining, but it honestly captures the decision making that goes into purchasing this library.