It's not fair to compare this to EDDM. The whole point of my site is so you dont have to mail to "every single door".
For example, I have 2 landscapers using my service and they target based on home value because they know most of their clients live in houses > $xxx. They also exclude renters because nearly all of their clients are homeowners. If they were using EDDM they might pay a bit less per postcard, but they would be sending to houses that will never signup for their service, so the actual CPA is higher
You mention "printing adds a bit of cost" but if you look around you will see that it adds quite a bit of cost. It depends on how many pieces you are sending but it could be .25 cents or .40 cents for 500-1000, or more -- but you have to send to an entire route, where you can send to a single house with my service.
Also, with EDDM you either have to batch your mailings per route, and deliver them to specific locations for USPS distribution, or pay extra for a print house to do that for you