100~500 ringgit is normally shit jobs/desperate people/very inexperienced people.

e-commerce sites cost usually four figures to five figures. for a site that sell their own things, maybe about 100 items it could be around RM3k ~ 7k.
if you are talking about sites like ebay, it will cost a lot more.

note that what i say is only an approximation, and it includes custom changes (minor ones)

thats up to you =)

exactly. that is why being a web designer is not so easy that you can just charge cheap. its just simply not worth it.

and respect to ur friend. 6 digits

that kind of script is usually in the tens-of thousands to 6 figures.

that is why most people just create one themselves, if they know how.