Headline writers always need to frame things like that. Every new phone is an "iPhone killer", every new electric car "should terrify Tesla", every new launch company is "taking on SpaceX". It's incredibly tiresome, to be honest.
Their engine (which is clustered in a group of nine on the first stage and one vacuum optimized on the second) is LOX/Kerosene and electronically fed. The electricity is stored in batteries.
SpaceX delivers about 150 times the payload at under 13 times the cost comparing the falcon 9 standard payment plan to the electron minimum. But that's irrelevant; they deal with different classes of satellites.
A better comparison would be of their rideshare (piggyback launching) programs but I haven't found their respective pricings, if published.