The stock market price for natural gas is around 200 $ / 1000 cubic meteres. And that's what russia is asking from the ukraine.
Certainly the gas prices of different sources are different but prices are made on the stock market and don't differ that much. It's similar to the oil prices.
Strong differences can be found where deals are made like russia does with e.g. Belarus. Belarus is still embedded in the socialistic (or watever one calls that system) market structures and sells products to russia well below market prices and thus pays only about 60$ / 1000 cm³. It's like a compensation deal.
The Ukrainians are on their way to break loose from that system (orange revolution) by doing so they e.g. sold steel ovens to an indian steel giant now producing with the up to now highly subsidized ng from russia.
Russia never intendet to subsidize Indian steel production and I don't see anything black mailish about asking the proper prices.
O, people, chill down. There's no need to get hysterical.
On the one hand, pacta sunt servanda, but on the other, vae victis. It's business, nothing personal.
P.S. There wasn't any genocide of the Ukrainians in the early 1930s. The Russians suffered just as badly. It wasn't intended massacre at all. It's simply accelerated industrialisation; centuries of enclosures, poor laws, hangings and transportations condenced into one decade.