Good day,
I highly recommend Not to use community forums (as this one) for LICENSE questions.
It might look like we understand since we orders several dozens licenses ourselves, but I learned that this subject can be very complex and you better read the small letters and understand it 100% before you recommend someone. These are matters of law, not just technical data, and I recommend to ask Microsoft license department directly.
If you are in north America, then you need call 1-800-426-9400, Monday through Friday, 6:00 A.M. to 6:00 P.M. (Pacific Time) to speak directly to a Microsoft licensing specialist, and you can get more detail information from them.
Worldwide customers can use the "Microsoft Licensing worldwide" Site to find contact information in their regional locations: https://www.microsoft.com/en-us/licensing/worldwide
With that said, here is some answers/info
How much it cost
In this link you can get the exact prices of SQL Server 2019
https://www.microsoft.com/en-us/sql-server/sql-server-2019-pricing
Note! For using Client Access Licence (CAL), you also need one server license. Therefore, According to the price list on site, for example for 2 users you need Server + two CAL which cost about: 899 + (2 * 209) = 1317$
how sql standard CAL will work on single PC
Microsoft has a special site for SQL Server licenses info. For full understand of licenses check this :
https://www.microsoft.com/licensing/docs/view/Licensing-Resource-index
Licensing briefs provide in-depth knowledge of licensing topics
https://www.microsoft.com/licensing/docs/view/Licensing-Briefs
Note! SQL Server 2022 should be released this year and it might be a good idea to wait for it.