The cool thing about cheap sea drones is that they are still incredibly expensive to operate. Like, the only cost center they remove is the crew which is negligible compared to fuel, transport, and equipment.
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.
"Exclusive: Saildrone Scores $37M BPA with USCG" <https://www.tectonicdefense.com/exclusive-saildrone-scores-3...>
"Saildrone Surveyor USV Market Research Report 2033" (2024) <https://growthmarketreports.com/report/saildrone-surveyor-us...>
My estimate may well be low. Ukraine's SeaBaby drone boats are reported to cost ~$250,000:
"Sea drones: What are they and how much do they cost?" (2023) <https://www.bbc.com/news/world-europe-66373052>