I saw some companys, they offer $9.95 per month for 500M web space, 5 G data transfer. is it possible for them to have any profits?

Probably not; if someone uses all that bandwidth.
But, they're banking the person that orders the plan isn't going to use it all.

thanks for response.
assume we don't talk about bandwith, just say web space...did they earn any money.
if they don't, why they exist in the market for so long....how they feed theirself....:o

Most peoples sites are less than 500kb each. Sometimes they will have a DB that is bigger or some downloads. But seeing as the hosting company won't let you put illegal mp3's or movies on the server, it's not likely someone will come up with 500mb of files, unless it's like freeware games, or a software company. They play the numbers game, average person will not use anywhere near 500mb. So they make money on the people like this, that don't use the full resources.

I think a lot of companies price their lowest plan very low because they don't expect the customers to use everything.

Hard Drives are cheap nowadays. So, costs for web space should not be a problem.