We have learned that it is far, far cheaper from a manpower, political cost and even materiel standpoint to ship a fuckton of MANPADS. Which are coming to Ukraine from the US, the UK, the Netherlands, Poland and Lithuania, just from the first page of Google results. Costs as much as a C-class: Costs as much as an off-shore drilling rig: 
It occurred to me that there's been few discussions of the fact that the Soviets/Russians never really got the hang of good ole American-style asymmetrical warfare. Overwhelming warfare? For sure. Level Aleppo, that's on-brand. Stack patriot bodies for the protection of the Motherland against the Hun? Russian through'n'through. But "I'm going to hang out in an air-conditioned booth outside Vegas while my remote control plane burps contrast-guided missiles at you half a world away?" They've never really gotten a hang of the whole "freedom fighter" thing, either. If the Russians or Soviets are supporting a political faction, they give 'em tanks. They give 'em APCs. They give 'em rifles. They give 'em truck-mounted surface to air missiles. you know, army stuff. This whole "we're going to give you everything man-portable well past the point of plausible deniability" thing just ain't their jam. This has the potential to be Afghanistan, except instead of poverty-stricken factionalized mountain tribalists they're going after the former industrial heartland of the USSR. It'd be as if Viet Cong tactics were adopted by Michigan against an invasion from New Jersey.