Another aspect is that buying old airframes from the Ukraine, who is going to support them, provide spare parts?
If you think the Ukraine could do that then they would be keeping them for themselves as their cheapest option.
If you expect Russia to provide spares support for Ukrainian planes then they wont make any money from selling the planes so they would need to make a higher mark up on the upgrades and support and spares.
These MiGs and Sukhois wont be anything like the ones you already have, and the first thing you will need to do is give them an expensive complete upgrade, because the money you will be saving by buying cheap old planes is all the upgrades and improvements that actually make them worth having.
That is why the Russian planes you buy cost more because while they are also old stock, they need complete upgrades and overhauls to get them to a useful standard level that India would find useful.
I wouldn't touch them to be honest, but I suspect the anti Russia mafia in India will leap on the idea.
Cheap planes sounds like a great idea that is easy to sell politically, and when they go to Russia to get upgraded and overhauled so they can actually be useful the cost required to make them comparable to the MiGs and Flankers you are already be using will probably work out more expensive than just buying from Russia... Russia makes money from the upgrades and overhauls, not from the old stock aircraft... that just saves them storage costs. For the Ukraine they need to make as much money from these old aircraft because the next step is buying expensive western ones... the US will likely give them great loan conditions... they always do to countries, because that money can only be used to buy US military equipment... but when they fail to pay the loan and spares and support cost more than the planes.... well Ukraine doesn't need an airforce anyway right... they can be like the Baltic countries and ask for HATO planes to patrol their airspace.
A little sad really... like the old English land owner family with the 40 year old range rover and the 50 year old Porche... but they have all this land and this huge manor house but no income... the house is falling to bits and they have to sell the Porche for a fraction of what it is worth to pay maintenance on the house so it doesn't collapse. The Americans have offered to sell them Lamborginis, but they will end up with something old and crappy like F-16s... block 2 or so... and that will cost so much in maintenance and fuel that it will sit in the garage gathering dust.