Since 2012, some 2,500 French communes have grouped together to form just under 800 "communes nouvelles" (new communes). This status enables several communes (known as "fusionnantes" or "historiques") to combine and form a single administrative entity. The budgetary issue is often raised by the elected representatives behind these mergers. This article develops an approach for compiling and analyzing data to study new commune budgets. Firstly, it asks whether communes that merge are similar to others in terms of the structure of their expenditure and revenue, and secondly, what changes can be observed (endowments, expenditure) following mergers. The aim is to question presuppositions, such as the idea that new communes have a particular profile or that they enable economies of scale. Using an original database, presented in the article and made available in a spirit of open science, we arrive at several results. Firstly, the merging communes do not have an entirely specific profile, and the group of new communes differs little from the group of all French communes. However, certain budgetary variables (rather high endowments and rather low staff expenses) seem to characterize the communes taking part in these mergers. On the other hand, although this is a widely-held and promoted idea, the transition to a new commune backed by national policies does not allow us to observe "economies of scale" across all budgets. The budgetary approach does not allow us to observe the reality of municipal services, but the budget lines, on a like-for-like basis, do not show any savings overall. In fact, there has been an increase in certain expenses, in parallel with a rise in government grants.