It's hard to find if you live outside Klang Valley. Not many shop carry Blade sparepart. And aftermarket part is not that much too. Well since I've never changed anything major so these are the only original part prices that i know

i) Engine Oil- Depends on brand..I'm using Agip 10w40, RM35/bottle. Blade use 2 bottle (1.5 liter only actually)
ii) Oil filter-RM12
iii) Clutch lever-RM40
iv)Side mirror-RM410 for both (crazy naza!)
v) Brake Pad-RM50/piece..Blade use 3 piece, 2 front 1 rear
vi)Front mudguard-RM99

So far I'm doing regular maintenance only, change EO+oil filter, 10k km changed spark plug, 20k km changed air filter.. Every time service around RM85..
Cost of maintenance for Blade 650 and ER6n will be higher of course 

If u want 250R i want to let go mine 
some said better take the facelifted version, lol not actually facelift only change new color, which is 2008 and above.
My personal FC on Blade 250R is full tank around RM30 (17 liter capacity) RON95 can get 402.2km...after that my bike die on the road side 
Speed between 130-140km/h..

zx2 is a good stable bike. kinda heavy for cornering but still rempit-able.

yes it have superbike like sound as its a 4cylinder 4stroke bike (not twin cilynder like the ninja 250 and er6) but the piston is very, very small. around the size of 50cent coin. so reliability at high rev is always the issue. and due its a very old bike, spare part can be quite pricey.

performance is around the zx150, ninja250.