I have quite a large collection of fountain pens but none is really expensive. As they are mostly vintage some may be worth something but I didn't pay a lot for them and I restore them myself. Probably the most expensive modern pen I have is a Waterman Carene. Nice but not wildly expensive. The pens I keep as opposed to those I sell, are because they are good writers in one way or another.

I don't use ballpoints at all. I do have some gel pens but they are rarely used. I address letters with the pen I wrote them with and I protect the address with beeswax. If I was forced to use a ballpoint, under duress and with thumbscrews, I would settle for a Crystal Bic. They do the same job as any other ballpoint, even those costing high three figures.