Are Facebook Ads not a viable channel for Saas?

I get that we're all bootstrappers here but I'm willing to put some money behind my product. Is there some reason (aside from the financial commitment) as to why we don't see ads discussed more often?

My one hang up is that I'm selling a $10 or $30 p/m product (with a 14 day free trial),. Perhaps the reason I don't see it often is that at that price, it's just a really hard solution to make work?