What is the autocomplete google service cost?

Question

Google Maps

Friends, the task was to implement auto-completion for entering an address / city to the user.
After certain searches, I settled on the google JavaScript Maps + google Autocomplete option, because. the customer needs international auto-completion of addresses.
I can not figure out the cost of such a service from Google. This page has a lot of pricing information
https://cloud.google.com/maps-platform/pricing/she...
There are links for different data types - basic data, + places details and so on. But somehow in some places it is not logical, or I simply do not understand the essence.
Why, for example, on this page - https://developers.google.com/places/web-service/u...
SKU: Autocomplete - Per Request($2.83 per 1000) is cheaper than SKU: Autocomplete without Places Details - Per Session ($17 per 1000), although the second option lacks data from Places Details.
What is the difference between Per Request and Per Session ? How is a session limited and counted?
In general, the main question is how many free requests you can get for a bunch of JS Maps + Autocomplete per month at current prices.