The protection is to prevent people from deleting rows or columns, inserting new ones, or overwriting them. That irreparably breaks the spreadsheet macros, rendering it and your work useless. We'd then get support requests to "fix" the pricing system, wasting hours only to discover that the person who created the spreadsheet broke it. Hence the password protection.
With that in mind, you can open the sheet in the free OpenOffice app and uncheck Protect. Fair warning though, if you break it and bring support into the picture because there is now an issue, you'll get charged support time if it takes more than 15 minutes to fix, and when we find the macros were broken this way. So please exercise prudence and caution. Widening a column is fine or adding rows to the calculator area. It is highly recommended to make a copy of the excel file before you unlock and make changes.
The password to unlock a pricing calculator worksheet downloaded from Pressero admin is shown below, spelled just like this and with the spaces:
pricing calculator worksheet