@rw
If its just for diagrams and random scribbles you really dont need anything too fancy. 50$ on a twsbi diamond with an EF or F nob shoukd do you good. But of your willing to go up to 300$ you can get a pen with a nocer case than that, even a gold nib. Pilot falcon will be the a good deal nicer, gold nib, stiff enough for scribbles but with just enough flex to see a roi shoukd you want to play with it and get fancy. Its a nice middle road pen that is an all rounder with high quality nib. These are my two favorite non-superflex nibs.
@freemo many thanks for the guidance.
@rw
Anytime
@freemo mostly scribbling. I sign my name less and less these days and when I do it is usually at the motor registry and they force me to use the hideous pen there.
As for fancy writing. Sadly my penmanship is more akin to a spider crawling across the page than actual writing. It is on my very long list of arts to work on, but if I am realistic I will just be scribbling notes.
Price wise... between about $100 and $300 would be a sweet spot. But always happy to save a bit or pay a little more if there is something good which would otherwise be just out of reach.
The only other element is feel in the hand. Years ago I had a pen with a nice feeling nib, but it was a screw top and the screw thread left an unpleasant groove in my fingers after long periods of writing.