I'd like to know which country/region has a low average of >$400K/y for a SWE so that you'd be "lucky" to find one for less. I know we're well paid, but definitely not that well.
The rule of thumb I have seen is that you should charge around double the hourly rate when contracting compared to what you would make on salary to account vagaries of contracting. So this would be closer to $200k given that rule of thumb.
It's contract work on the US west coast. Typically 3-12 month projects bringing some obsolete system into the current decade.