My assumption is that if someone's building an engine that will cost $6-8K in parts not including the oil system, that "affordable" means "affordable for the owner". My next question would be can one have a 2nd engine built from the ground up for less than the cost of the dry sump? How about even 25% of the 2nd engine's cost? If not, I'd say the cost is affordable but hard to stomach. Maybe the sticker shock can be mellowed or justified by looking into the power a good oil system frees up, or thinking about how important it is to protect that overall engine investment, or how important it is to continue to race without worrying about the reliability of the engine.
Like everything else for a car: "Speed costs money Son. How fast do you want to go?"