Far from identical. 300 is a new bike (new fairing, new chassis, etc), but with a bigger FI 250 engine. The 300 also have a slipper clutch.
In NA the 300 replaces the carb 250 (300 is FI and at least in NA, the 250 is a carb bike). I think in EU the 300 replaces the FI 250. In Japan the 300 and FI 250 are sold at the same time.
Yes, it is rather confusing…
My bro got a 300 recently.
Was at Phibbs today, a $4799 stand color Ninja 300 OTD price would be around $5500! That is with $300 freight & prep, tax, DMV.