Elon Musk once said Tesla's FSD would only get more expensive. The automaker just slashed the price to $99 a month.

• Tesla slashed the price of its assisted driver software, FSD Supervised, from $199 to $99 a month.

• Elon Musk once said the cost of Tesla's FSD would only increase as it improves.

• The discount comes after Tesla missed earnings expectations for its first quarter.

Tesla announced a price cut for its assisted driver software on Friday amid lower-than-expected vehicle sales for the first quarter of 2024.

A subscription to Tesla's Full-Self Driving software — now called FSD (Supervised) to remind drivers that the system requires their attention at all times — is now being offered for $99 a month, down from $199 a month.

It's just one of a few recent moves Tesla has made to hook more people onto the company's Level 2 self-driving system, which requires a driver to constantly monitor the vehicle.

Elon Musk recently mandated all Tesla employees in an internal memo to take new customers on a "short test ride" of FSD before handing over the vehicle during the delivery process.

His rationale was that "almost no one actually realized how well (supervised) FSD actually works," according to the memo that Business Insider confirmed.