Home Depot [homedepot.com]
has EGO 21" 56V Lithium-Ion Cordless Self Propelled Mower w/ 7.5Ah Battery for $549 in select regions. I was able to get this price at the Santa Fe #1505 store in Denver CO, but have it shipped free to me in CT. It is listed as $599 near me. Not the largest discount, but it seems like $50 is about as good as it gets for the self-propelled model.
I was also able to chat with a rep to apply my 15% movers coupon to the order as it seems to be the "regular" price in this region, and not a sale price.My total was $466 + tax.