I think perhaps Myer is struggling as a retailer, so they are having sales often...

I know that for toys such as LEGO and Transformers, while they tend to have more stock than Kmart, the latter usually has better prices. Even when Myer has a LEGO sale, sometimes the prices at Kmart are still lower.

The one thing that sets them apart is Myer's access to LEGO Creator Expert sets, however they are often excluded from the toy sale.