To be honest I wouldn't skimp and scrap on a light for my bike.
Defo +1 to that.
Apologies for posting this again but I think it's very relevant here.
Some comparison photos, all taken at fixed exposure, against a £20 CatEye, in this case an HL135.
Cateye HL135 on its own
Cateye HL135 bottom left, against Exposure Joystick on high, the Cateye has all-but disappeared
Cateye HL135 bottom left, against Exposure MaxxD on high. Yes, the Cateye is still turned on, you just can't see it any more.
Save your money and don't buy cheap lights.