I suggest you read some newspapers which make sense.
The American difficulty as of now is not financial, but related to design and technology development. America started the 5th Gen race, the Russians were far behind. When the Americans were out with F-22, the Russians were developing Su-30 and Su-35, The Russians felt that perhaps the technology required for 5th Gen plane need to be more mature. Even Russia was coming out from break up of USSR and almost all developments had come to halt due to lack of budget. This thing now is thing of the past. When the Russians took over Crimea, and EU and USA sanctioned Russia, some of the western financial papers said that in few months Russia will collapse. Are the few months up?
The Russian difficult at present is mainly the engine, izdeliye 30 This is the real engine being developed for PAKFA
The other engine which is being used now izdeliye 117 it is only for Testing. It is the engine used by Su-35S. So using that engine, they can test the other avionics or weapons which are not directly related to the engine. Skills is never a problem for Russia, If you notice than Sukhoi company has sold more nos of Su-27 and su-30 than Rafales. So, its actually that inspite of this "less budget" they are able to produce and sell more planes than Dassault (incredible no?) and they are having more variants of the plane than Dassault (wow) and further, they are developing and building own 5th Gen plane which unfortunately a developed country like France cannot afford. Developing a 5th Gen plane now will bankrupt France, because they know the orders wont be coming. So whatever "5th Gen tech" they are developing they dont have a 5th Gen plane to put it in, so they now pimp rafale as a "5th gen plane." which it is not. And just to make a point, Sukhoi is also incorporating the 5th Gen tech they are developing into Su-35S, Su-30 SM and other variants so that these planes are the top of the line of 4th Gen planes. The Russians dont pretend that adding 5th Gen tech to a 4th Gen plane will make it 5th Gen unlike the French.
Russians have huge oil reserves and oil is going to be in good demand, now and future. Why would they worry?