I'm not sure about USD price, but it's actually ~600k xby for lvl 1 nodes. There is a 100k fee (which you can't get back) on top of 500k (that you can sell anytime by breaking the node) plus 100xby for the transactions. There will also be lvl 2 nodes which should be ~250k each?

You can break nodes at anytime and get your 500k/250k back!