Your alternatives for supplying gas to Europe couldn't meet demand. Cost would obviously increase cause of high demand with little supply. With high prices and little supply, Every country would want to maximize its oil and gas reserve use so would your alternatives sources.
Russia supplies around 200 billion cubic meters of gas to Europe every year (40% of the total demand). If you take the supplies from the alternative sources (US LNG, Venezuela.etc), the spare capacity is less than 10% of the amount provided by Russia. On top of that, new regassification and LNG terminals take at least 5-6 years to build. To complicate things further, the Biden administration has taken many policies that negatively impact the shale oil and gas producers within the United States, ever since he took office in 2021 January.