If I've read the CAA information correctly, in the year up to 31st March 2009 (most recent available) Jet2 made a profit of about £23 million (before taxes). For comparison, in the same year, Monarch made a £70 thousand profit (something for the Monarch thread Jet2 bashers there!), easyJet a £92 million profit, Flybe a £16 million loss, and BA made a £454 million loss. Someone do correct me if I've read the wrong figure though!
http://www.caa.co.uk/docs/80/aln_fin...count_2008.pdf