A: You will be able to add as many users as you want after you have reached the maximum 10 in the AppSumo deal. The cost for the PRO plan is then $12 or $18 per user and month, depending on purchase per month or per year.
If you are a larger enterprise with many users, it is worth considering the Enterprise plan where Cultup also gives more consultancy support related to measure and working with the organisational values.