I'm in the UK. Our trains are expensive, much more than the rest of Europe, but we have Megabus and Greyhound which are pretty well priced. I've researched BlaBlaCar for getting home to my family and it's comparable to a Megabus. Roughly speaking, BBC/Megabus will be £10, Grerhound/National Express (nicer buses) will be £20, and trains will be £60 (or £40 for young people). I've never heard anyone mention BlaBlaCar here.