You undoubtedly got great deals, I was still a Mazda dealer when the Diesels came out and what a miss on Mazda's end for that car. It came too late, too expensive and in my opinion, without enough torque grunt which is synonymous with Diesels. I loved my 2015 Golf TDI I bought right before Dieselgate (and was bought back by VW as a result). I had to go deep to move one of them (not as deep as your deal) but lucked out with a service customer who fell in love with my other in Soul Red and took it for invoice less the $5k in rebates Mazda had on them.
Again, my only caveat I want to point out for people reading this thread is your deals, while for sure highly discounted well below cost, absolutely had rebates involved in getting your deal. My statement still stands that 15% is virtually impossible to find as a base dealer discount, save for super rare circumstances (like a super low allocation product flop like the Diesel). For everyday Mazdas, no one will find 20-30% off from purely a dealer discount perspective.
Why do I care about this distinction? Because if people are using this thread to negotiate and shop for a new car, I would hate to see someone walk on a great deal because they misunderstood and think a dealer could possibly discount 20-30% plus rebates on top.
Happy shopping everyone
-Matt