The flash new signs at the mouths of four arterial roads leading into the city came at a cost of $860,000.

The federal government chipped in a quarter of a million dollars to install the 'Welcome to Canberra' and 'Sister City' signs through the Tourism Demand Driver Infrastructure initiative but $610,000 was stumped up by the territory government.

The signs were unveiled last August on the Monaro, Federal and Barton highways as well as Pialligo Avenue, just weeks out from the start of international flights between Canberra, Singapore and Wellington.

Chief Minister Andrew Barr said at the time the signs offered visitors an "impressive welcome to Canberra".

However ACT Opposition leader Alistair Coe said the price was "outrageous".

"We want to make sure Canberrans are getting the best value for their dollar so when we see over $600,000 being spent on eight signs, it is reasonable to question what sort of return we are getting," Mr Coe said.

"Given the signs are targeted at people already in Canberra, they're going to have marginal benefit for our economy. The money would be better spent on promoting Canberra interstate."

An ACT government spokesman said the cost covered the design, construction and installation of the custom-made signs and was determined through a competitive tender process.

He also pointed to the significant size of the signs - they stand at 6.2 metres by 3.3 metres.

"It is not uncommon for cities to display welcome signs," he said. "These new signs are an impressive welcome statement for visitors entering our nation's capital, something that is particularly important given the recent increase of international visitors to our city following the introduction of international flights.

"Tourism currently contributes $2 billion to the ACT's economy and employs 16,400 Canberrans. These signs were designed to last a number of years and can be reskinned with new images in the future."

However Mr Coe said the linking the sign spend to tourism was tenuous.

"Given the signs aren't seen until visitors reach the border, you have to question how effective they are in attracting tourists," he said.