Wiki has AIM-9X at 0.4 mill back in 2019 and ESSM at 1.8 for 2021. Not sure how accurate those numbers are and of course they've grown with inflation, but alot cheaper than an SM. If you only adjust for inflation values from 2019 to 2024 its right around 0.5 mill.
I feel like an IR tracker would work better on cruise missiles than laser guidance but could be very wrong. IMO one definite advantage of AIM-9X to APKWS is the range to me, I'd rather engage the target 10 miles out if protecting a ship vs 3 miles out. The 70mm rockets are great for a cheap ground defense not sure I'd trust the defense of a ship with them though.
I do agree we need a cheaper solution to go with missiles, either it being ALAMO or HVP and a soft kill like HPM or lasers. 3 layers for a good layered self defense bubble. My thinking with the drone with AIM-9X was probably cheap and quick to do for a quick capability add while getting the rest of the defense layer figured out.