The barrows is a good way to make money. And if you use the Slayer dart spell, the only think you're really paying for is the Prayer pots. But if you're good enough, the racks, extra runes, and ocasional item more then makes up for it.
Heres something I figured out about it also.
Kill Count 7 = Minds, Chaos, Death
Kill Count 10 = Chaos, Deaths, Bloods
Kill Count 15 = Minds, Chaos, Deaths, Bloods, Some Times Bolt Racks.
So if your using the slayer dart spell, you just get the kill count for what ever runes you need. Heck, I did it so much, I had 20k Mind runes.....then I died with 10k of them on me
Oh well, they're cheap anyways