Like others have said, 2008 and early 2009s are very likely to burn oil. I think Kawasaki worded it best on their website when the 2008 came out "New ring design for improved oil consumption". You can take that 2 ways.
All will use some at high RPMs... the nature of a big thumper.
My 2008 burned oil early, but didn't meet the 1L in 1000miles that Kawasaki required to do something about it. Mine only burned 850mL in 1000miles at in the first 10,000miles
I recently did an Eagle Mike 685 kit. Budgeting $1000 is about right to do it right. I spent more, but did other things while I had it apart and necessary at 26000miles (some unnecessary). I always kept my oil level good, and my head was in good shape. I did get EM to refrub the head though.
Some observations from my original head/piston. The goop on top of my piston wiped clean. it was burning so much oil, it was as if the oil was steam cleaning the piston. The piston rings were not at a 12, 6, 3, 9 O'Clock as they should have been, but more like 1, 3, 2:30, 2 o'clock. All the gaps were in the same vicinity. I sent my head and cylinder to EM and he sent off my cylinder to get bored out. His guy that does that for him said that my cylinder was already too large to bore the 2.5mm for the 685 kit and they were wondering if I had already done an overbore, but my engine had never been opened up.
I don;t think the 685cc kit gave mine more power... just freshened it up, returned it to it's normal power it should have had, stopped the oil burning and made it a bit more smooth.
If you can get a really good deal on a 2008 or 2009 that will cover the $1000 and your time to do the top end and are OK with doing the top end (it's not too difficult and only took me 2 Saturdays in between the wait for parts and machine work), I'd bo OK with one of those years... otherwise Avoid it.