We need to maintain our current policy to have 2 different set of fighters. It's too risky to have just one. Any problem on the supply (parts/missiles/etc) for whatever reason (technical, political, etc) will cripple our air force instantly.
So far we have been managing the U.S. and Russians sets very well. If we want to phase out the Russian ones and stop importing them once and for all, then we have to start looking for the alternative to replace them.
European jets will do nicely. It's obviously easier to manage the U.S + European ones compare to the U.S. + Russians.
Building new infrastructure is off course costly. Initial investment in almost any kind of sectors always needs more money. That's why we have to make sure it's worth it.
Just compare all the future development and replacement of any European jet alternatives that we have now. Pick the best of the bunch.
(sorry I don't really trust our KFX program for now)