Video: Negotiate with Your Doctor and Cut Medical Costs
Bear in mind the "up to 75%" can mean anything from zero to 75% - so if ANYONE saves any money they are being "honest".
This outfit, from web reports, apparently sends out many of these type cards to millions of people. It is not clear where they make their money, but one thing to bear in mind - going through them likely gives them all your personal ID and medical info - which might then be sold who knows where.
Basic rule - if you did not contact them first or ask a vendor/contractor for advice or a visit, assume they are up to no good - sad but safe.