South Australian Premier Steven Marshall says Australians returning to Adelaide from overseas will be forced to pay quarantine costs from Saturday.

Australians returning to Adelaide from overseas during the COVID-19 pandemic will be asked to cover the cost of their 14 days of hotel quarantine with a family of four to face a $5000 bill.

Premier Steven Marshall says the fees are about recovering the cost of keeping returned Australians isolated from the wider community and are not about turning a profit.

The fees will come into effect on Saturday with the first person to be charged $3000, their partner a further $1000 and then $500 for each child.

"We are still keen to assist with the national repatriation program, but taxpayers will not be footing the bill going forward," Mr Marshall said on Monday.

"Anybody coming in from overseas will be required to do 14 days of supervised, mandatory quarantine in a hotel and now they'll be getting a charge for it."

Mr Marshall said any Australians still overseas who wanted to return had been given ample time to do so.

He said the state government would consider payment terms and cases of genuine hardship.

"But the reality is people have had plenty of time to get back to Australia," he said.

"There's some real stragglers at the moment and they'll need to be paying for the costs that are incurred by the taxpayers."

The premier said a question mark was also hanging over SA's timetable to lift border restrictions with NSW and the ACT on July 20 given the concerning cluster of cases linked to the Crossroads Hotel at Casula.

"We've got to have a very close look at what's happening with that cluster, that's raising some real queries," he said.

"We've just got to see if there is a significant escalation between now and the 20th of July.

"But if it's not safe to lift our border restrictions then we will not be doing so."

Hotels, pubs, and nightclubs also remain a concern in Adelaide with one slapped with a $5000 fine for failing to have a safety plan in place.

Images from the nightclub showed large numbers of people in close proximity with little scope to socially distance.

Police conducted checks on 111 venues over the weekend and found 10 operating without safety measures.

Mr Marshall said it was incumbent on all people and all businesses in SA to do the right thing.

"We want to keep this horrible disease at bay. We've got an obligation to keep everyone in this state safe," he said.

"Those that are doing the wrong thing will suffer the consequences."