I am not sure they do. They probably are just using Google Vision API as a regular customer. The pricing will change if Google had to do a legal deal with these folks.
Defending on the service provider, there may be an upfront cost for signing a BAA, but generally the service costs remain the same (assuming you stick to "BAA approved" services). In the case of Google, there is no additional cost:
"As such, we can offer HIPAA regulated customers the same products at the same pricing that is available to all customers, including sustained use discounts. Other public clouds charge more money for their HIPAA cloud, we do not."