Based on my past ownership of ZZR250 and Versys650, yea almost same.

Engine oil - 2 botol for both
Oil filter RM30 for 250 RM50 for 650
Petrol 1 tankful about rm26 (given same fuel price) gives me same mileage of 300km, mixed city and hiway riding.
O-ring Chain & sprocket set same for both about rm300+
Tyres 1 set - about RM800 for my 250 and close to rm1k for the 650
basically that's where the similarity in terms of upkeep and running.
it is no brainer for me to pay the same running cost but doesnt get the same enjoyment. so i chose to upgrade.

roadtax is RM50 for 250 and RM250 for 650

power wise 250 is a high revving engine, gotta really throttle it to enjoy the speed - just like kapchais. stock standard condition - u wana go 120 on meter the rpm is already 8k, redline at 12k. u get about 160 tops, 170 maybe in rare occasion. On the 650 going 120 engine rpm only 6k+. squeeze it up to 9k, u get 160 on meter. redline at 11k and u get about 180... on the Er6 where the tuning is slightly different, u can touch 200 at 12k... u run the engine (both 250 & 650) at high rpm for long term, wear and tear is faster - eventually u need to do valve clearance and top overhaul much sooner. so might as well get a bigger one and running the engine un-stressed  at 120-140 so u can ride it long term without much issue.

plus, bigger engine can carry load better than a small engine could and at the same time relatively economical. just an example, back then in 2009 when i was riding to Betong with a friend, both of us carry pillion. he is fatter and heavier than me. i ride zzr 250 while he rides a zx9r. we both fillup full tank in Rawang and rides at the same speed of 120kmh together. when we reach tapah, i have to fillup RM15 for full tank, and he only needs to fillup RM9. simply because for his engine, he is riding at mid-low rpm while i am riding at  8.5k (considered high) rpm.

but then again, for work commute and if your gaji ciput like me, 150cc below is the perfect bike in terms of running and maintenance. everything is cheaper by a large margin compared to 250cc and up, just that on the speed department need to adjust expectations lah. 150cc can run 110-120 but again at high rpm. keep it 80-100 then basically it will be trouble free and safer to boot.

I changed Naza Blade 4x times edi.. 2x 250 2x 650
I would say go for the 650.. because the weight of bike is almost the same so you will have less power on the 250

Value for money bike i would say, enough power for everyday commute, even for weekend fun

None of my 4 bikes had any problem, never need to leave in workshop whatsoever