It cost me a fair bit to pass my test...
CBT - £90
Theory - £31
DAS - £420
Mod 1 - £15.50 (which I failed) Mod 2 - £75 (couldn't take as I failed Mod 1)
Mod 1 - £15.50 (passed!) Mod 2 - £75 (failed )
Mod 2 - £75
So, bear in mind you're not guaranteed to pass first time, it can become expensive!
Then theres all the gear... budget at least £600
Its great fun though, good luck with it
ps. I got a Yamaha R6 for my first bike, its awesome but I messed up and came off it 2 weeks after passing my test. My advice is take your time and don't get over confident, you'll get bitten in the ass if you do!