are individual writers too expensive than the big companies?
Depends on the company, depends on the writer, depends on the turnaround. It's true that you pay for quality, but you pay for reliability too. In my opinion, the ideal scenario would be for someone you know to refer you to a high-quality freelancer. If you don't know anyone who can vouch for a freelancer, the equation becomes a bit more complicated.
There are steps anyone can take if the want to try to verify that a company is reputable--these forums are a good place to start. But there are scams everywhere, and it can be hard to sort fact from fiction, irrespective of whether you're dealing with a company or a freelancer.
At the end of the day, you have to roll the dice. If you feel you're overpaying, then look elsewhere. But if you're getting quality work already, the cost of trying to find another reliable source--sifting through scammers, possibly paying for a product that comes back in broken English, etc.--could end up outweighing the money you hoped to save by changing in the first place.