Earlier quoted context omitted.
Buk isn't a "cheap and cheerful" alternative to S-300. Soviet air defense doctrine was a multilayered approach featuring systems at almost every organizational level from infantry squad up to theater. Buk and S-300 serve at different organizational levels. Both are competent systems and ironically are probably more effective against Soviet derived air forces than western ones. Starting in WW2 and moving forward each…
It's wild how many anti-air systems they have deployed, for an almost non-existent enemy air force. At this point they must be effectively supplying the enemy their SAM systems. Very expensive, too - saw a $15M system ditched in a field because the shitty KAMAZ truck carrying it broke its axle.
The other reason is if things go south and the US/EU decides Putin is bluffing on the nukes, they'll for sure wish they had it because NATO aircraft would color the sky gray.