About $ 90 million is necessary to complete the construction of the aircraft. Taking into account the aircraft testing costs, this sum increases up to $ 120 million.
That is surprisingly cheap for such a large plane; compare Boeing's freighter prices:
One of the captions says the An-225 Mriya is designed for 5,000 flights. The thing holds 100,000 gallons of jet fuel. Assuming it used 70% of that on average, that could be over a billion dollars in fuel over it's life assuming $3 per gallon.
747 prices have gone way up over time, way past inflation rates comparing newer models to old, but they have also improved fuel economy tremendously.
(also, is that $120 million inflation adjusted? And is it just the cost of modifying the aircraft it is based on, or the cost including the base aircraft?
That isn't the price from 0 to flying; it's apparently already more than half built. I'm also not sure how accurate that number is; different reports state numbers between $100m and $300m.
Well, that's 180m in today's dollars, not to mention when you buy a modern plane you're paying for ultra-efficiency, modern avionics, modern safety standards, etc which increases cost, the same way you could buy a deathtrap muscle car in 60s that got 15mpg that is cheaper than a modern car. I'd rather take a cross-country trip with a Prius than a 1960's GTO. I'd rather get into a serious wreck in one as well.
Also, the lifespan of this whale is 8k hours. The lifespan of a 747 is like 100k hours. This seems more like a research vehicle than any sort of cost-efficient production vehicle. My understanding is that it was designed to transport the failed Soviet space shuttle clone.
That is surprisingly cheap for such a large plane; compare Boeing's freighter prices:
http://www.boeing.com/boeing/commercial/prices/