Convert a spreadsheet into a tour quotation calculator

This project is to develop a database / website solution that will calculate the cost of tours that my company runs.

At the moment I have two spreadsheet objects.
1. A spreadsheet that acts as a database of supplier rates. There is a separate spreadsheet for each calendar year.
2. A calculation spreadsheet, that I make a copy of for each quotation that I need to calculate.

The calculation spreadsheet allows the user to enter the services (such as hotel rooms, transport, activities and guides) that clients use or consume on each day of the tour.
Based on the data in the Rates Spreadsheets (for the applicable year) it works out:
• How many of these services are needed (so for example five clients booking together will need: One vehicle that seats 5+ clients, two double rooms and a single room in each hotel, and one restaurant meal each).
• The cost price of supplying the services for any number of clients
The costs are then marked-up to calculate the selling price of the tour.
There are some special cases with additional logic built in such as calculating a price to charge per client when there is one complimentary place per x clients, costs of rooming when all clients must share only with someone of the same sex, discount pricing offered by suppliers for children, groups etc.
The spreadsheet contains all the logic that I need. However, it is cumbersome to use and very difficult to maintain the databases of supplier prices.
Protected versions of the spreadsheets are available for download from my OneDrive folder at https://1drv.ms/u/s!AoRTvyHPs6BxhSjUUL3o8uxSajrv?e=CHK0xO

This project is therefore to reverse engineer the spreadsheets with the calculations (and options) that they comprise and create an online database solution that will calculate the price of tours.

The solution will need to be user friendly so that it can be used by non-technical staff with the system guiding the user though both data entry and maintenance of the database of prices as well selection of relevant services as components of a tour so that they are associated with the correct dates.

The result of the calculation is the price per person for running the tour.
The final output must be clearly shown and associated with the details of tour that it represents, so that comparisons and changes can be made. Version control of instances of any quotation would be a valuable feature.

Initially the system can operate with a single user account. Ideally using a Google login.

Upon successful delivery of this requirement, future enhancements will be requested including allowing "What if" scenarios, supporting allowing multiple user accounts and potentially creating a subscription based web app. These can be discussed in more detail in due course.

Interested developers will be invited to an online meeting when I will explain the way that the spreadsheets work in more detail and how the solution will need to work. After this meeting a selection will be made, and unprotected copies of the spreadsheets will be shared. However, almost all the logic has already been worked out, it just needs to be converted into an easy to use, professional working system with a modern intuitive feel.

I have a Google Workspace account, so use of Google Cloud Services is preferred to keep everything in the same domain. Ideally a future version could be made available as a Google Workspace App.