Without knowing which companies your refering to, I would say that anything which seems 'too good to be true' is probably a scam, or at the least they'd be giving you traffice which isnt relevant to your service. Remember just because you get traffic, doesnt mean you'll get sales. I would concerntrate on a strategy which you have more control over. This may take longer, but think about it, if you could pay $50 and get so much traffic then why isn't everyone doing it?

In a nutshell - be cautious!

Later

i think its a fake

I try not to use these companys as i think they are a waste of money and dont bring good traffic to your site!

Few reputed and reliable company give guarantee for bringing traffic to your site like studiotraffic. If you select most reliable and capable company after thorough review, you are not going to waste your money.

i think they get traffic via traffic exchange system or something like that

All those tricks are nothing more than marketting gimmicks to capture the client and then make money.

Practically just you think yourself that how it is posisble to attract 10000 visitors for $50 .If it was so simple that probably every body would have spent that amount .

Just go deeper and under stand the process , truth will come out .There is no short cu t to online success.

Yes it is possible. Seen pop-unders and other deceptive ways you get re-directed to some sites? That's how you get this traffic. :p

From my tests (and of others too), this traffic is the worst at getting converted. In fact, most of these traffic companies would actually not send you real traffic but script generated traffic.

I'd suggest investing this money into PPC search marketing rather than these traffic packages.