We paid a lot of cash for Highcharts (Highstock actually) a couple of years ago as an up-front investment for a process manager we were building - an OEM licence. This was about a month's salary, straight after I quit my FT job. The product is now ready to go live almost three years later, and there still isn't a charting library, free or otherwise, that offers us the same functionality that this did back when we licenced it.<p>Not to mention the fact that the CTO himself will fix bugs for you within a week or so if you ask him nicely. Great company and great model. I don't get how people can complain about the fact it costs money. The costs are passed on to your client who will gladly pay for a better product, and you're supporting the ecosystem. I'd have paid double what we paid.