For many gastroenterology procedure needs, you can use colonoscopyassist.com
Colonoscopyassist.com provides information for accessing much more than just colonoscopies. You can search by procedure and by location, and you will be provided with options in your area as well as a cash price.
Example services and prices (there is some variation in price depending on location):
Colonoscopy: ~ $1,250
Endoscopy: ~ $1,250
FIT test: ~ $50
Cologuard: ~$600
Hemorrhoid banding: ~$500
Are you a provider? Claim your practice here