The ones 1970-01-01 mentions are sail-driven and solar-powered. They can operate autonomously over wide-ranging areas for years.
Saildrone have produced at least 24 vessels: 20 in the Gulf of Mexico, four in the Baltic, and possibly others. There's a tender of $37 million with the US Coast Guard, and a market of $412 million as of 2024. This suggests a unit price on the order of about $10,000, which is downright cheap for any seaworthy craft.