Low cost and dentistry are (usually) not expressed in same sentence.
Greenville has a community health clinic named "New Horizons" that now offers dentistry on a sliding scale fee. Click "New Horizons Dental Care":
Services. Here is a pdf sheet on their dental services:
http://www.newhorizonfhs.org/dental_services.pdf.
However, I would first call any private dentists in your local area and inquire about "self-pay" rates. Most (if not all) will give discount rates if you are paying in cash.