[darkgael]

I very much enjoy .410s. I own a few and shoot one or another regularly.
For me, the only advantage of the .410, though, is that they are lighter guns and easier for me to carry in the hilly uplands of PA. They are way less forgiving than a 12 or a 20. I shoot 16 yard Trap with mine fairly often (I am not a great Trap shot in any case) and I know that there are shots that are misses with the .410 that would have been powder with a 12.
Beginners gun? I think not. A beginner wants to, needs to, see a positive result and the little .410 just does not throw enough shot nor provide the pattern consistency that the larger gauges do.
Lower costs? Have you bought any .410 ammo lately? Generally, .410s are a few dollars more per box than equivalent 12 ga. I reload mine.