I've lost too many EDC pens to spend a lot on them. Here's my story.
I like fancy pens, but have been disappointed in some build quality and maintenance required (specifically for fountain pens and calligraphy pens). I used to write a LOT. The most expensive pen I purchased was around $300 (Waterman fountain pen), and a gold piece fell off of it a few years after purchase (I never tried to send it in for repair). I fell out of love with fancy fountain pens and calligraphy pens because the fact that you have to clean the nib everyday or so, maintenance I didn't want to invest my time in (and if the cap fell off in pocket you are screwed). For writing 10+ pages of notes or papers, I ended up purchasing Pilot Dr. Grip gel ink pens and pencils, and haven't looked back since.... that was about 15 years ago and I still use them today and refills are readily available and reliable.
Moving on to smaller EDC pens, I lost a Fisher Space Pen, then replaced it with a mini Cross collapsible gel pen that had a key ring that I really liked. Unfortunately, the mini Cross gel refill cartridges are hard to find and the generic refills didn't work half the time. Also, EDC'ing a pen meant that it accumulated a lot of wear and tear from rubbing up against keys and other things in my pocket. I later purchased a Fisher Space Pen that came with a keyring on the cap for keychain carry.
It was just too big for what I wanted on my keychain, so I moved it to a Victorinox Belt Hanger with chain with some other mini-EDC items.
I used that for a few years until I went to an EDC pouch (small camera belt pouch I put my EDC things in). Currently, I'm trying an inexpensive DIY mini pen which slides into my pouch and only cost me a couple pennies. It's basically an inexpensive Bic pen you can purchase in bulk or usually find for free lying around. I cut it to size for my pouch, but have seen people cut it down further for putting on their keychain. You can also drill a hole in the end to put a keychain ring on. Here's mine:
I cut the end of the white area nearest the writing tip. Then 30 seconds on some sandpaper to clean it up. I also had to cut the ink insert with a scissors (a little ink will leak during the cut). So far no issues, and it hasn't leaked ink from the cut ink refill for the month that I've been carrying it. Just another option that might be fun if you like inexpensive DIY projects on the cheap.
In the past, I used to peruse
Mont Blanc,
Waterman, and
Parker pens. One trick for Cross pens, is that Marshalls and/or TJ Maxx will often get them in at certain times of the year and they are significantly marked down.