Professional voiceovers should cost more than five dollars.
I wouldn't expect quality from anyone that would do a $5 voiceover, and I'd be insulting a professional to ask them to work for that price.
That's free market economics for you. You also get what you pay for.
Most of those I found at fiverr are recorded at home and not in a good studio setup. For simple voice overs for selling those $1 ebook etc, fiverr is good option. But for a bigger business, its better to look else where.
Price level change in Voicebunny according to market conditions, and they will get a bit lower in time, but I´m pretty certain that the fiverr talent is not very professional..