Fortunately for Claris FileMaker users, options are to purchase perpetual licenses which last so long as the client OS (and /or server OS) allows, or pay-as-you-go monthly or yearly which includes ongoing upgrades and for the app and OS. Options also include either hosting the app on premise or the cloud, your choice.
Still dependent on a 3rd party. Choose a nice cross platform spreadsheet format, easily transfer that from one spreadsheet program to the next (or even to a different OS, providing make sure font and/or formatting transfers, which shouldn't be that much of an issue, but there are outliers.
In far less time than attempting to replicate an estimating app using spreadsheets, one could create a genuine and efficient database using the appropriate tool such as FileMaker. FileMaker has legs, spreadsheets not so much.
Well, if we are going to add something like SQLite like to the mix. A little bit of python (I try to avoid it as much as one can, I like my compiled languages, but it is one of the easier ways to get into this) and easily have something running with SQLite. If on
Windows (I use Arch by the way, despite the meme, I cannot not say that), TKinter comes with the
Windows version of python and that is supper easy to work with, if wanting to get that complicated. Now, yes, it will take a bit longer with adding something along these lines, but personally, the older that I get, I hate being anymore than I have to be subject to someone else even with regard to the world of open source. After done with all of that, use Pyinstaller and create a binary to take it to another
computer that doesn't have python installed and run it. Python does have a speed problem, but in most instances, it's fast enough, and with the ability to quickly prototype and get something going, that's enough for most people.
Personally, I prefer to do things in C/C++, but Python is going to be more realistic for most people, getting up and running quicker and not have to worry about dealing with the extra dependency of SQLite as well.
Most any estimating database accommodates the major bookkeeping solutions in some way or another.
If that is needing from an estimating software, can easily handle that using CSV files (what I use for my wife's accounting software), however, be aware that depending on the accounting software, some have very specific formatting needs for the CSV files that one imports. I believe Quickbooks is one of them.