Vapor has nothing to do with data hosting costs and DDoS. It solves the problem of data ownership, incentive, monetization, etc.
This difference in the interpretation of what benefit decentralization provides is why many past "decentralized internet" projects have focused on the networking aspect (censorship resistance, DDoS avoidance, etc.) whereas Vapor is taking a different approach where it tries to solve a different problem. Its main focus is to decentralize the power structure, and to do that it needs to solve the data ownership (both philosophically and technologically), as well as frictionless monetization.
The goal is to change the power structure that drives the web, and I believe it has more to do with how the data itself is structured (so that it can be distributed trustlessly regardless of the network) than the network stack.