A couple or three additional thoughts.
You'll often get widely divergent experiences with lower priced pens. For example, my Kaigelu 316 was complete junk. Gold plating shedding off the bottom of the nib, nib and feed tending to come out if you screwed down the screw in converter a little too hard. Cap would not post, although that's a feature rather than a bug, and many here are adamant about never posting their caps. On the other hand, a lot of people really do seem to have had better experiences with it than I. You pay your money and take your chances.
Although restoring vintage pens can be very rewarding, I don't know that I'd recommend a first try at it as a gift for someone else. And if you plan to have someone else do it for you, then you may have trouble coming in under $50. Some older cartridge/converter pens may require no restoration beyond a cleaning, the same for some old squeeze fillers, like a Parker 51 aerometric.
I don't think anyone asked yet, but is the intended recipient of the gift already a fountain pen user? If it's someone who already knows something about fountain pens, then picking something that will be appreciated for itself may be trickier. Of course, they may still appreciate the thought.
"So convenient a thing it is to be a reasonable creature, since it enables one to find or make a reason for everything one has a mind to do."
- Benjamin Franklin