We use Excel to consolidate and manage IT budget figures. The annual amount is approximately 30 billion yen. Because many people use it, there are problems with getting accurate figures, such as degradation and errors in Excel functions. We think that dedicated budget management products like Apptio are too expensive for our budget scale. We would like to consider what other options are available. What tools does your company use to collect, consolidate and simulate IT budgets?

There are a lot of tools.
Not sure to get how many people get their hands on your excel and what exactly is « managing budget ». However if more than 20 people, or if you are in an ITFM program, complexity is always something with the best excel sheet.
At some point, did you consider using some classic Reporting tools like ERPs (Oracle, SAP), EPMs (Hyperion), or PPM tools (Clarity, Smartsheets, Planview, Triskell, … there are many). Also now service management tools are offering that kind of functionalities (Servicenow SPM).

We currently use a combination of Excel and Hyperion (but we aren't using Hyperion to its fullest potential so I would sadly say we are primarily Excel-based). Our goal is to move to Oracle EPM Planning and Budgeting most likely in the next year or two since we use Oracle Cloud ERP as well as Oracle EPM's Account Reconciliation module. I assume EPM Planning and Budgeting may be outside of your your budget scale then as well, although I don't know how expensive Apptio is.

I understand your frustration with Excel, we typically have other users provide their portion of the budgets to one person who manages the workbook and pastes the provided worksheets into the workbook. We allow others to see the workbook on a read only basis only. Hopefully others will give you other good ideas for managing your budget that fits your budget as the day we move from Excel-based spreadsheet budgets will be an exciting one, and I am sure you will feel the same way.

In the interim, while you are finding your ideal software, consider using Excel best practices such as locking down sheets as much as possible, having just a few "owners" who are allowed to make changes in your main workbook, save copies of the workbook often so you can return to a prior state, if needed (we are lucky that we use SharePoint so it has document history and you can return to the state prior to any corruption or mistakes). There are also good tools out there to clean up Excel before it becomes corrupted (usually the corruption I have experienced comes from too many styles within Excel and compatibility issues. There is a free tool you can get at the Microsoft Store called XLStyles Tool UWP that I would run periodically on the spreadsheet and it will cleanup all of the nonsense styles or objects that don't work such as named ranges and links. The first time you try it, you should do it on a copy of the file so you feel confident using it but it has done wonders in lessening the amount of corruption my large files have encountered.