I don't now why there are so few 8 speed road bike brifters. I assume its because when they came out with 8 speed road bikes, 9 speed came along very very soon thereafter hence they just stopped making them and went right to 9 speed stuff. There are a LOT of 9 speed brifters and components. If price is important, I would go for 9 speed stuff. Most 9 speed consumables aren't that much more than 8 speed stuff.

I would just go for 9 speeds and look at it as the good balance between parts availability and cheapness.