Highest price you should pay is $150.
Even if those SLAs have no cycles on them, they get saggy after a year or two.
Components on the bike are pretty mediocre and heavy. The motor itself doesn't have much potential either, and the controller is locked out of higher voltages if it's an 08+ which it sounds like it is.
I had one for a moment and it wasn't too bad, ended up getting rid of it because i wanted more power and the hill climbing ability was kinda blahse.