Mec has a kit for loading .410.

Parts are easy..............
it is the primers and the lead shot that hurts your wallet.

Hulls, powder and wads are not bad, cost wise, if you shop around.

8lbs of Promo if you can get it, was the way to go for cheap 12 Ga. loads.

410 Alliant 410 cheapest........... H110 case life doubles.
Good luck.