This price drop is due to price matching Mighty Ape who have reduced their price from $59 to $55 and now $49 + $5.90 Delivery.
If you already preordered on Amazon in the past, you don't need to do anything, as per their pre order guarantee, when it ships you only get charged the cheapest price it was listed as.
Release Date - 04/09/20
Edit 4/9: Released, no longer preorder. Amazon remains the cheapest, however if you want it today JB Hi-Fi $54.