If by now you've browsed a number of websites that offer thesis and dissertation research assistance, you have probably seen a range of prices. The low-ballers offer prices as low as $10-$15 per page. The higher-priced services get $60-$70 per page. Some people simply choose the service that gives them the best price.
The danger of selecting a thesis or dissertation research assistance service based on price is obvious. How can can any business produce, say, 240 hours of research for $15 per page? This would mean they pay their researchers $3 per hour. Nowhere in America are those wages acceptable. If a service seems too inexpensive to be real, it means the work is being performed in Pakistan, India, or the Philippines. In fact, many of the services that advertise on Google are based in other countries.
So forget the cheapies. Once you've gotten up to a reasonable wage (at least $30 per page), you have to consider who will take care of you best--in short, who you can trust. Thesis and dissertation research assistance is, for the most part, an unregulated industry. So it is your consumer responsibility to ONLY deal with services that have phone numbers. Before making such an important purchase, you should have real human contact. Ignore testimonials and quotes from well-known publications on the website. Those can easily be made up.
Once you have reached a representative from the thesis or dissertation research assistance company, speak with them for a few minutes and see if you feel comfortable. A good rapport needs to be established before making any sort of commitment. In the end, the service you choose will simply come down to a feeling.