The Financial Conduct Authority (FCA) revealed under a Freedom of Information request submitted by City A.M. that it ran up a bill of £40,722.68 for scoping, overseeing the review and appointing a so-called skilled person firms to carry out the report.
These costs were incurred between when it was announced the report was being carried out in January 2014 and when a summary of its findings was published last November.
The figure refers to external costs incurred by the team working on the project, as the regulator did not quantify its internal costs. However, the watchdog estimates the hours spent on this piece of work is equal to roughly two full-time staff.
The FCA also did not provide the cost of the report itself, which was carried out by "independent skilled persons" Promontory Financial Group and Mazars, as doing so would reveal confidential information about other companies.
It has been claimed RBS routinely forced distressed small businesses into its GRG unit, so the lender could then profit by charging high fees and snapping up properties belonging to the troubled firms at rock-bottom prices.
The FCA revealed last November the report examining the allegations lobbied at GRG had discovered no widespread evidence of misconduct, although it did identify some shortcomings, such as substandard communication with the customers assigned to the turnaround division.
The bank has also recently set up a £400m compensation pot for small businesses which have been caught up in the scandal.
The announcement of the review's findings was a long time coming. The review, which was formally announced by the watchdog in 2014, was sparked by a 2013 report from former government adviser Lawrence Tomlinson.
The FCA declined to comment further on the costs.