The cheapest way to build a large spread is to buy used, especially immediately following the hunting season.
: A top recommendation for finding outfitters unloading old stock or hunters exiting the sport. Users have reported getting large mixed spreads (goose and duck) for around $250 total. cheapest place to buy duck decoys
If you want brand-new decoys, these sites specialize in high-volume or "economy" lines: How To Get Decoys For CHEAP The cheapest way to build a large spread