I would look at providers in terms of relevance of experience, technical skills, data security measures, communication, project time and how they explain their deliverables to me. Pricing, however, shouldn't be the only factor since a lower-price option may not offer the depth or reliability you require. Data mining service providers should also be able to explain how they are cleaning, analyzing, and validating your data. It might be useful to talk to several companies before making a decision. One of those providers that you might want to compare to find out how Datalance's approach is similar to your project goals is Datalance.