I don't quite remember, but e.g. this online shop https://www.hashop.nl/Shuttle has them for e460 = USD533 (includes 21% VAT). But it must depend on the length, and on whether you need special shapes (e.g., I have two bay windows), so YMMV.

Sounds like a lot of money, but out of all automated things, the curtains are the things of which I most often think 'that is very convenient, glad I spend the time and money'. Most other HA things are fun to play with, but not really all that important (in my experience).