I don't disagree about the DSG service cost adding up over time, but at $350 it wasn't unreasonable. I actually liked the fact that VW wanted the transmission serviced every 40k miles as I think it may help longevity. We generally keep cars until their bitter end, so I'm all for reasonable maintenance.
I'm not 100% convinced in the no-service interval for the Mazda transmission. By the way, the FZ fluid from Mazda is about as criminally priced as the VW DSG fluid. I plan on a drain and fill around 40k miles, at the same time that the spark plugs have to be replaced. Luckily NGK recently introduced the 2.5 turbo plug for purchase as NGK rather than Mazda dealer only, so the cost per plug is around $15 instead of $25 from the dealer.
We looked at A3 and A4 as well this last time. I like the styling and smaller size of the A3, but A4 is a much better car. I think Audi, MB, and BMW tend to cheap out a little too much on their smaller cars. Except for the M2, nothing cheap about that one.