Please take your time to read the below otherwise click elsewhere. I will try and make it short but I feel I need to explain the situation fully so that you guys can help me decide whether my quotation is on point.

Hey guys, I'm glad there is a place on stackexchange to ask this question.

I have a great client, our business relationship has extended for a year now and I've offered him two solutions for his two businesses. I charged him £9k each. Everything went smoothly both iPad based applications were completed. 

I flew to my client's country to take down all requirements in full for the third project. A full electronic college application. Then he realised that it needed to be put on hold and instead he would need a payrolls application for the college first since he makes payments to his staff members every month and the majority of his payroll office have quit knowing that it will all be electronic based in the future, hence the urgency for the payroll application.

Now, its a bummer because it does mean the price I wanted to charge will have to be reduced since hes reduce the project scope. This project will include the following:

* a Biometric system that will interface with my application, it will clock in and out staff members attendance for payroll. These machines would be laid out around the college entrances and exits, and at the security office for security staff to clock in and out too.
* client's iPad will display dashboard data, how much money he needs to
pay his staff members at the college, in cash and to the banks.
* There would also need to be another module at the payroll office where one staff member can check exactly which staff member is owed how much cash, with a printer printing out invoices/a little staff payroll sheet that will print that the cash was collected.
* a timetable module for the head teacher of the college to be able to see all staffs time tables for when they should be in and when not.
* To be able to edit staff's working hours.

For this project application for one business only he will be quoted around £23k. 

This is fine, however I received a call a month ago where he's requested for these additional features.

* He now wants a centralised payroll system for ALL of his businesses, (theme park, college, food company with head office and factories, hotel, and the future hotels that he is building) each business have staff members ranging from 30+ staff members, to 200+ staff members.
* To be able to add biometric machines in the future, as many as he likes, that can be placed in his future businesses and any new businesses that he starts up.
* To be able to monitor his range of businesses from his app all in one place.
* So he can continue to implement a biometric full system in every single new business he opens with this application.

This is then means that he would no longer need to come back to me everytime he wants to implement a new biometric system for his other business and future businesses since my application would now be able to handle new biometric devices being added.

This is like an unlimited license that he's asking for. How much should one charge for a situation like this? What should be my multiplier?

Here's what I dont want to do:

* Charge him for every new device that's added into the system say £2k for every new device. That's silly for me.
* I also don't want to charge him for every new business he wants to extend the application for

So I have decided to give him a one of fee, the question is how much? I have thought about multiplying the original price by 2.3, £23k x 2.3 = £53k. 

And thought of increasing maintenance by £2k increments for each new branch he extends within the app for every year after his initial 1 year free app maintenance.

Am I charging too much or am I charging too little for this unlimited license?

**UPDATE 1**

In regards to one question from one of the answers: The businesses that he will continue to install this application for will be his own businesses so that he can monitor the accounting information that would be automatically tracked. The information that will be tracked is how much to pay his staff members each month through the biometric system that he wants to continue to install and monitor in his future businesses to come.