If you put the Amazon link to the Rotring 600 pen into CamelCamelCamel and wait a bit you can get a brand new one for less than $24. I got one just recently for $23 and change. Suggest the Schmidt EasyFlow 9000 refill or if you want a gel, then the Monteverde Capless Ceramic Gel
Well before Christmas they were selling the Rotring 600 off Amazon for less than $30 and the Rotring 800 for less than $40. I think the Schmidt EasyFlow 9000is the smoothest writing hybrid ink out there, even smoother than the Jetstream, IMO.
Now everyone on Amazon has raised their prices for the last minute shoppers, however delivery promised by Dec 20 if you order today (Dec 18).
Define Affordable - IMO one of the best is the Rotring 600 - $26.58 - It is slender and has a knurl grip. It is my go to ballpoint pen with the 9000.
If you put the Amazon link to the Rotring 600 pen into CamelCamelCamel and wait a bit you can get a brand new one for less than $24. I got one just recently for $23 and change.
Pen - takes Parker compatible refills like Schmidt EasyFlow 9000 - my favorite.
If you shop Amazon, use CamelCamelCamel and get the Rotring 600 ballpoint pen. If you put in $24 it will be a week or so and you will be notified that the price has dropped and you can order. I cannot say enough good things about this pen but all are over $30+ now/well today but the price changes all the time. The seller I linked you too is where I bought a silver one a couple weeks ago for $23.
Hope this helps.