Alright: it's USD480/year (plus administrating those two servers) vs. USD58/year but no, "cost of servers/internet isn't a reason". Ok, great.
Cost $0 if you have some old stuff lying around + the power they use.
Cheaper and just as good. The chance of both providers going down at the same time is pretty slim.
Heck, I'll host your secondary if you want it for free, it's not like I'll notice the bandwidth. Primary is different because you'll need access, secondary is just a bunch of lines in a conf file, it'll update when your primary does.
mail me at j@ww.com if you want to take me up on that offer.