Pricing considers two main factors.
Firstly, how many existing seats do you have in your plan?
Secondly, how many courses do you have in your plan?
It is the combination of courses and total number of seats that will determine how much your plan will cost for a 12 month subscription.
If you only want additional people to train in the courses you already have in your plan, the cost will simply be Additional Number of Seats x Current Plan cost Per Seat.
If you want to have your current team gain access to courses not currently in your plan, the cost will be Total Number of Seats x New Plan cost Per Seat. You will only pay the difference between what you current plan costs and the additional amount of the new Plan.