The Texas State Comptroller has approved the payment of $29.3m towards costs for the United States Grand Prix at the Circuit of the Americas.

State Comptroller Susan Combs approved the payment from the State's Major Events Trust Fund, which is financed through taxes generated from certain major sporting championships or events to pay costs incurred hosting them.

While the organisers had sought $30.6m, the $29.3m, which comprises $25.3m from the state and $4m from the city of Austin and which was paid last Friday, goes a long, long way to covering not only the hosting fee but also such things as traffic management and temporary grandstands.

However, it's claimed that original estimates of the impact of the event may have been exaggerated and consequently Combs' office is to carry out a thorough investigation within the next 18 months and will use the findings to more accurately release funds in future.

While a report by Smith Travel Research showed that between Nov. 14 and 18, leading up to the race, hotel revenue was $32.7m, around three times the revenue from the same period in 2011.

However, some businesses, including restaurants, claim that trade fell off during the race weekend, hence the claims that the forecasts were over ambitious.

"I think in promoting the event, and also promoting the event to produce the yield out of the Major Event Trust Fund, they just hyped (economic projections) into a zone of unreality," Richard Viktorin, a CPA for Audits in the Public Interest, told KXAN.com. "And, that's where the dashed expectations have now come from."