Page Comparison

It's free and works out of the box subject to some limits:

2500 requests per 24 hour period.
50 client-side plus server-side requests per second.

Limits are raised for "Google Maps API Premium Plan" customers:

100 000 requests per 24 hour period (default limit).
50 server-side requests per second (default limit).

Pay-as-you-go billing:

$0.50 USD / 1000 additional requests, up to 100,000 daily.

Google is very clear that caching the results is allowed and recommended:
"Whenever possible, pre-geocode known addresses (using the Geocoding API described here or another geocoding service), and store your results in a temporary cache of your own design."

The Semarchy xDM Google Maps Enricher does not have caching built in. But using the Semarchy xDM Lookup Enricher, it's straightforward to implement caching if desired.

Authentication for Google Maps JavaScript API

Customers should add their client ID, provided by Google, when making the API call to display a geocoded Google map. Google also requires registering authorized URLs after adding the client ID, or else the map won't display.

Authentication for Google Maps Geocoding API

The Google Maps Geocoding API is a service that provides geocoding and reverse geocoding of addresses. This is the API used by the Semarchy xDM Google Maps Enricher.