I cut about 2 acres of grass. In four years, I have put 60 hours on my 54" Bad Boy ZT. I do not keep track but estimate less than two gallons of gas per hour. 15 hours a year works out to about $100/year. Add in an oil change every two years for $20. $110/year.
Ego 10 Ah batteries cost $200. If they last four years, $800 every 4 years. And the Ego will not mulch leaves like the gasser will. If cutting 30 times a year, an electric might cost less but I only have about 15 cuts a year where I live.
The Bad Boy should last 30 years with my use. I am in my seventies and will never need to buy another ZT. The Ego looked a bit flimsy to me but should be good for most lawns. My lawn is reclaimed forest area and a bit rough in spots so a heavier duty machine made sense.
One size does not fit all.