I don't believe the physical antenna itself is difficult or expensive. The expensive part is all the digital phase control circuits that are needed to actively

I don't believe the physical antenna itself is difficult or expensive. The expensive part is all the digital phase control circuits that are needed to actively steer the antenna beam. A electronically scanned array antenna is actually a whole lot of little antennas fed by an equal number of phase control electronics. The phase control electronics need to be small and inexpensive (since there are a lot of them) and also able to accurately adjust the phase of a very high frequency signal (24++GHz). That is difficult. https://en.wikipedia.org/wiki/Passive_electronically_scanned_array https://en.wikipedia.org/wiki/Passive_electronically_scanned... Example pulled from a google search: https://www.fairviewmicrowave.com/sma-8-bit-programmable-phase-shifter-6-18-ghz-sdps-0618-360-sma-p.aspx https://www.fairviewmicrowave.com/sma-8-bit-programmable-pha... $12,000 (less in quantity ;-)