Galileo in HyperChange said that he called a broker just to know the price of borrowing Nikola shares, and they said that it's 200% APR if I recall correctly. It may have been direvtly after the merger though, I don't know the exact details.
You can actually look this up! IBKR provides SLB (stock loan borrow) rates for users, and someone made a site to report this data. https://iborrowdesk.com/