By Aditya Soni (Reuters) -Tesla shares jumped 10% 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.

The service kicked off as scheduled aboard Tesla's Model Y vehicles, with customers paying a $4.20 flat fee to ride.

Tesla rolled out autonomous robotaxis in Austin on Sunday to a limited group of testers. CEO Elon Musk said in a post on social media platform X that customers were charged a flat fee of $4.20. The launch puts Tesla head-to-head with Alphabet-backed Waymo,