The new centre at Giant's Causeway has attracted 117,000 visitors since it opened at the start of last month.
The popularity of the interactive experience at the World Heritage Site on Northern Ireland's north coast has exceeded predictions, said site manager Alastair Walker.
MP Ian Paisley Jnr has said the £8.50 charge for adults is excessive, while one Canadian visitor said he was told he could not get into the souvenir shop without paying and complained that signs at the centre are misleading.
Mr Walker said visitor numbers speak for themselves. He said: "It is beyond our expectations but we are managing it. It is something the area has needed for the last 12 years since the fire (at the old visitor's centre in 2000). We have got it now and we cannot do it for nothing.
"There are significant overheads to the building and because we are supported by the rest of the National Trust, the money raised here goes into work on all the other National Trust properties."
There are signs letting tourists know the causeway itself can be visited for free, Mr Walker said. The admission cost is competitive when compared with other attractions in both the UK and Ireland, and includes parking, audio guides and walking tours, he said.
Giant's Causeway Visitor Experience costs £8.50 if you drive in. It is £1 cheaper if you come by bus or public transport, or if you use the park-and-ride in Bushmills. It costs £4.25 for a child and a family ticket costs £21. National Trust members go free.
Mr Paisley, a DUP MP, said he was contacted by constituents who describe the pricing plan as excessive. He said: "It potentially makes Northern Ireland's most popular tourist location less popular."
The MP previously lobbied on behalf on private developer Seymour Sweeney who wanted a rival visitor centre at the causeway. In June Mr Paisley described a decision by the National Trust to mount a legal challenge against another project he supported, a golf course close to the causeway, as "a national disgrace".
The causeway is a Unesco World Heritage Site and features around 40,000 interlocking basalt columns formed millions of years ago by volcanic activity. The £18.5 million centre was opened by First Minister Peter Robinson and Deputy First Minister Martin McGuinness on July 3.