If you fly to and from Moscow as often as I do, you will have noticed what a big difference in prices you can get in you book and issue your ticket outside Russia and if you issue it inside. A 25-30% higher fare for a ticket issued in Russia is commonplace, even if booked abroad. There are not many airlines flying into Moscow and connecting with big European hubs: AF, LH, SR, SN, BA, AZ, KL are the most important. All of them, except LH and SR have a single flight a day, always B737 (AF, LH, KL), A320-319 (SN, LH, SR) and the rare B767 (KL). Moscow has 10 million inhabitants and with this little amount of seats you can imagine the fares that are being charged.
For my next flight to Barcelona, SR SN have a lowest Y published fare of $575 without apt taxes, and the STAR group is even higher. AZ, KL and BA fares are never more than 20-30$ cheaper. I usually do not jump into conclusions, but I can only conclude that there is some kind of agreement between then so as to keep this kind of fares.
Of course Aeroflot flies Spain but not every day and the times are not always as convenient.
There are some nice surprises in the low months (February-November) but the rest of the time you can expect 650$ at best up to 1100$ for Y class. From any big European apt with real competition between airlines (AMS, LHR, CDG, MAD, BRU, etc) you can fly return to LAX and South America.
My advice: if possible, do not book your tickets in Russia if you have to travel there!