The savings _ from using your "in house" expertise _ in terms of money and man_hours alone, will quickly justify the investment you make in "developing the needed skills" _ especially, when you compare what you spend with the cost of purchasing a commercial software application _ or even engaging the services of an Excel VB developer.
Spreadsheet Tracking As A Crucial Element For Business Development. There are ways you can use spreadsheets to record and track materials usages/stocks, product sales, and other business data such that discrepancies will be easily detected when they do occur. The use of spreadsheets when properly done, can help to uncover the cause(s) of "losses" in virtually any aspect of a business operation.
This last point in my opinion is ONE major benefit you must seek to extract, if you choose to engage the services of a developer. S/he should be able to help you develop (in_house) expertise needed to maintain the application AFTER s/he is gone. If you fail to ensure this, all your cost_savings from using the application might end up being spent paying the developer to maintain the application over time in the future!
A DIFFERENT Type Of Automation. The approach to spreadsheet automation that I refer to, is one that seeks to provide functional spreadsheet automation alternatives for ANY spreadsheet user task(s). Typically, solutions like this would require the developer to study existing manual data recording, analysis and report generation systems, then plan _ in consultation with users _ for incorporation of automation into the spreadsheet to replace them, where possible.
types of spreadsheet
spreadsheet templates for tracking
what is a spreadsheet used for