Domains Live limit users and office 365

I have some domains to domains.live.com

The limit of the users is 50.

Fore some domains i want to have more than 50 users.

I searched the forum and there was some answers about Office 365.

I saw the plans about Small/Midsize business and Enterprise

for Small/Midsize business there were some plans with 5$/month and maximum users 25. So if someone needs more than 25 can he get more?

and the price will be 25 users x 5$ = 125$/month?

for the enterprise plan the packages starts from 4$/month

If someone needs 100 users than he will pay about 400$/month?