At times, they would prefer to click a button that says "Print ABC", or "Print XYZ" report, instead of having to crawl all over the huge spreadsheet(and get "lost" every now and then), to highlight and print different report pages. Using a custom built data entry form to make data entries into 14 different cells in different parts of a table(at the same time/with one click) would, for them, be "heaven" compared to making the entries one at a time.
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!
In addition, visualise it having dynamic query/report drop menu interfaces, and a variety of custom buttons: for navigation(within and between worksheets), printing, data export (as PDF documents or spreadsheet files), saving, auto_data filtering, auto_charts plotting, auto_backup of files, user login authentication (for documents with sensitive or confidential content) etc.
"Over_used/Over_spent"(Losses) and "Under_used/Under_spent"(Savings) _ on a monthly basis based on data entered, the program also automatically plotted charts showing trends over a 12 month period.