Although I don't have either a ball winder or a swift (yet), I have run this same discussion in my head. What I have come up with is that if I could only get one or the other, I think it would be easier to come up with substitute for a swift than a ball winder. If I was opperating the winder, I could slowly feed the yarn from the hank if wrapped around chairs, or some kind soul's hands. I'd review the subs for swifts that the creative types on KH have come up with to make it easier to make speedy use of the ball winder...
If you use a slow version of a swift, then perhaps a Nostepinde would be a sufficient "ball winder" ?
And if worse comes to worse, when you spend some of your 300 clams on yarn, have the shop wind it for you, if you plan to use it soon.
Just my 583 cents!