I've never owned a full-sized Lazer but my Lazer Z HP and my walk-behind Exmark have been excellent machines. The full-sized Lazers are the mowers of choice by many landscapers. That and Scag, and in my area Bob-Cats too. Exmarks have a fairly highly baffled deck that gives an excellent cut and fine clippings, but they tend to clog and spit clumps in heavy and/or wet cutting conditions. As far as hours go, that's a little high, but still less than half of the reasonable life expectancy of the motor and maybe 25 percent of the life expectancy of the machine.
My main concern would be the hydros. Make sure there are no leaks at all and that they operate properly and smoothly when the unit is hot. You could give it a quick test drive and think it's fine only to find that after 1/2 hour of use one side stops operating properly. They shouldn't "howl" either. Or the engine may run and start fine when cold and then break up and stutter when hot or not start hot. The same with the electric PTO- fine cold and disengages hot. This goes for any mower, not just Exmarks/Kawasaki engines. And a Kawi is always my choice too. I can't speak for that specific engine though.
Basically I'd want to run a mower like that through at least a half hour of mowing before bringing it home.