CBR 125 should be in the range of 1500-2200 depending on the year, milage and condition.
Ninja 250 is different.
Pre 2008s should be around 2500-3500. In all honesty, the ones that are above $3000 are pushing their luck.
Post 2008, the price can range from 3500-5000. People ask for anything above $4500 are absolutely nuts. Again, it depends on year, milage, condition and modifcations.