I heard a rumour that BigW might be $19 for the One-step, which is about the same price as the GEN Legends 2-packs.
As we saw with the Robot Replicas from the first two movies, Hasbro prices by size rather than complexity (perhaps the cost of design is negligible next to the cost of construction/labour/transport).
The Robot Replicas were just lumps of plastic with about 5 moving parts that didn't transform, but were the size of a Deluxe, so were priced like a deluxe.
The one-steps are close to the (now smaller) size of Deluxes, so it is actually surprising that they are so much cheaper (almost a third off the price of Deluxe).