Not that cheap is bad and expensive is better but given that the TS is asking if there is a possibilities of doing OW below $500, I guess we are just giving him some cues or advice, if you will on what to expect.
We all know that its unlikely to do OWD even with $500 in Dayang/Tioman. If there's any DC that can do that, then its better for him to be extra cautious and check thoroughly.
Who knows, he might get lucky and get a very good instructor for that amount. Well, even if he is shortchanged, he wouldn't know it anyway, at least till he start diving more often with other DC or friends.
It's a common question for most here in Singapore. Instead of asking which is a better DC, they will asked which is the cheapest one. Sad but true but I don't think we can change that cheap & good mentality here.
However, for people like the TS, he's making good effort to ask question on forums so I hope he take the advices and opinions positively. For us who have gone through this, please be gentle with your "advice". Share your experiences for him to learn and not scare him off ok.