The short answer
No. HighLevel includes unlimited users on every plan, so adding a salesperson, an assistant or a client's front desk staff does not raise the $97, $297 or $497 monthly price. What does add cost is extra phone numbers, per sub-account add-ons such as AI Employee at $50 or $97 a month, and the calls, texts and emails each person sends.
What unlimited users covers
HighLevel's pricing FAQ says that on all plans you get unlimited contacts and unlimited users, and it describes users as team members. That covers staff in your agency account and people inside each sub-account, so a client can give logins to its owner, office manager and receptionist without changing your bill. Access is controlled with user roles and permissions rather than paid seats. For a team of ten, the subscription line on the invoice is the same as for a team of one.
Costs that grow with a bigger team
The plan price stays flat, but more people usually means more activity. Anyone who needs their own line needs a phone number: $1.15 a month for a local US number or $2.15 for toll-free. Outbound calls cost $0.0166 a minute and texts $0.00747 per segment plus carrier fees. HighLevel's add-ons are priced per sub-account, not per person: AI Employee Growth is $50 a month, AI Employee Unlimited $97, WhatsApp $10 plus Meta's message rates, and the Branded Client Portal App $49. None of the published add-ons is priced per user.
The limit that actually matters
On Starter, the constraint is sub-accounts, not users. You get 3, which covers one business with room for a test account, but an agency signing a fourth client has to move to Unlimited at $297 a month. HighLevel prorates that upgrade if you make it mid-cycle. So when you choose a plan, count the businesses you will run on it rather than the people who will log in, then add each business's expected texts, calls and email to see the full monthly cost.
More answers in HighLevel questions. For costs, see GoHighLevel pricing or run the cost calculator.