I mean yeah I'd imagine buying Atamaca for 41 ships (each with no less than 2 or even more launchers) would cost a lot of $$$ as well.
Maybe 1/5th considering amount of man-hour and fitted electronics and less integration time.
For an AD system there will be a need for 3D search radar (NS50 minimum), mediocre tracking radar (at least one but can be omitted) added personnel (the weapon officer will be someone with knowledge of AD) at least 3 consoles - one for search radar, one for tracking, target information, commander etc - one for missile control interface and there can be more plus the CMS will be 'included in packet'.
Atmaca is; 1 operator console, not necessarily need of a CMS, same guy who earlier done ASuW on that boat, same commander.
If you desire to have an AD system on those ships, Mistral is way to go. One console and 2 of 4 tube launchers on forward and aft positions. You can likely shift the guy who has worked with manpads earlier as well. Low cost, ease of integration, ease of personnel rotation.