Well done, Zohan. Now take the time and "headache" to register a full auto machine gun or Short Barreled Rifle which is actually fairly painless and multiply it exponentially. You'll then be in the ballpark.
There are other factors at play as well but in the USA there are 5 N registered MiG 29s. 4 of them fly and provide services for the US Government. The other is registered to a museum.
Su-27s would be their own nightmares and since I haven't personally tried to import one and know only basics I'll defer to Bodhi, the expert in this instance, to answer if he would like.
There are major differences in flying vintage airplanes such as the MiG-15,17 and 21 compared to the various front line Soviet fighters of today. Same goes with trainers like the L-39/29. You can buy F5s, you can buy F-86s and T-33s with relative ease.
As time passes these things change.