Tesla launched its robotaxi service in Austin on Sunday as its Model Y vehicles drove around a select batch of riders who gave rave reviews about smooth, convenient rides that were available for the cheap price of $4.20 .

The company debuted its autonomous ride-hailing service Sunday. The limited program is invite-only and uses around 20 cars—signs that Tesla has a long way to go to catch up to its robotaxi rivals.

Tesla shares jumped over 9% on Monday after the electric-vehicle maker started testing its long-awaited robotaxi service, a key step toward proving the technology that CEO Elon Musk has for years touted as a crucial driver of its lofty valuation.