I had one month to write a GUI that would log and chart dozens of variables with tens of thousands of data points over long time periods for a new industrial process device, from scratch.
I tested several chart packages, and the only one that could handle that much data without choking was Nevron Chart. It does take some work to customize things, but I feel confident that everything is customizable if you dig deep enough. The way it scales and pages data by default is not quite how we need it - we need more hysteresis. So I wrote my own scaling and paging logic and plugged it right into Nevron Chart's scaling and paging hooks. That I could do that at all is amazing.
Everyone loves the GUI and even with all the zoom quirks it's far better than anything I could have written myself in the time given. It was absolutely worth it for cost vs man hours.