The "secret level 2" incentive requires owners to land five Model S and Model X sales to get behind the wheel of a TBM.

Tesla is apparently teaming with CEO Elon Musk's latest startup, The Boring Company, to provide a particularly unique prize for Model S and Model X referral sales.The "Secret Level 2" prize description promises winners "the opportunity to drive an electric tunnel boring machine with The Boring Company in Hawthorne, CA," according to screenshots posted by Teslarati.

Participants must complete the first referral level and land sales for an additional five vehicles to be eligible for the Level 2 prize.

Tesla is presumably hoping the prospect of a ride in the TBM will mobilize more owners to join in the Model S and Model X upsell strategy. Official salespersons are apparently under pressure to persuade Model 3 reservation holders to buy one of the more expensive existing models, which could help reduce the backlog of nearly a half million deposits for the mass-market sedan.

"Unlock new levels with every 5 referrals for an additional 2% off per referral and more amazing adventures that money can't buy," the Level 2 description adds.

The ultimate prize is a free Founder's Series next-generation Roadster.