Russia subsidised the cost to Ukraine. Now that will end.
discounted gas:
http://www.cbc.ca/news/business/ukraine-russia-cuts-off-cheap-gas-u-s-arrives-with-aid-1.2559449
“Concerns over Ukraine’s financial condition whose treasury account is, by its own admission, almost empty rose after Russian state gas company Gazprom said it would cancel a substantial discount on natural gas granted in December. President Vladimir Putin, meanwhile, noted Ukraine still owes some $2 billion for gas.’