Pricing after 10 free- incremental or back to user 1?

Pricing after 10 free- incremental or back to user 1?

I suspect I know the answer here, though it's never been spelled out.  Let's say I have the free version, and 8 people are able to use/see it (I'm just doing pretty basic customer database type stuff for our customers and end-users).  

Now, let's say I want to add some new people, and i go to 12 users.   In that case, would I have to go from $0/m0 up to $144 ($12 x 12 users) per month?    That's ~$1700 per year....and a pretty big step.  

zoho is just about perfect, with all the customization that i can do, for us.....and i'd be willing to pay.  however, $1700 is too much.  for that, Ill stick to a spreadsheet.

Thanks much in advance!