Without actual miles driven it's impossible to make a meaningful comparison. My wife spends less on her minivan than my EV - but she's not driving to work every day (and she prefers to drive the EV when she can).
Call me crazy but I suspect you and your brother drive a different amount. $100/mo in a Tesla I ballpark at driving 1900 miles per month, so you're probably driving less than him, unless you get more than 150mpg in your hybrid.