I purchased the kit in the box option as I'm a complete idiot when it comes to anything more complicated than Lego. I've not completed my kit yet, but so far I've spent about £1000 on top of the kit and the bike purchase (not including extra wing kit).
Now some of that was on tools, some on upgrades that I thought I'd do (such as the radiator, fuel pump, etc), and lots on bolts & pipework.
If you want flappy paddle gears for instance, you'll need to add an extra £800 or so. If you go the turbo route you'll have to upgrade some of the ancillary stuff so you may end up doubling up on some of things you have off your 'busa.
No instructions to date though, but the build manual from the Tr1ke will get you started. It's my first kit, but it's been a nice kit to work on, easy access, good quality bits and the factory support is good.