The article posted here is saying that narcissists tend to be less generous though.

“One (perhaps somewhat funny) takeaway message from our study would be: if you are choosing a date, beware of highly narcissistic men who are simultaneously low on baseline testosterone – in our studies, they were the least generous (and most selfish) in their decisions,” Czarna added. “They shared the least resources with others. So, when going on a date with one of them – prepare to pick up the bill. Meanwhile, men who were low on both narcissism and testosterone were highly generous.”

And agreed it also doesn’t establish how testosterone plays any role in this either, seeing as how both measurements kept the same level of testosterone and only adjusted for the level of narcissism (how do you even measure that conclusively). This is a really shoddy pseudoscientific study that just screams confirmation bias. No idea why they even included testosterone in the discussion when they didn’t identify any correlation.

On a side note, the “prepare to pick up the bill” remark is just kind of a gross and manipulative sounding characterization of what they are trying to say.