Those most severely damaged estimate bills for repairs and ruined stock could be as much as £1 million.
And some say overall losses, including lost sales, are still impossible to quantify – five months after the looting.
Duncan Mundell, 61, owner of Party Superstore which was set ablaze when rioters took to the streets of Clapham, south-west London, on 8 August, estimated his personal setback would be between £100,000 and £250,000.
He said: “It’s been an absolute nightmare.
“With the place burning down, all my staff out of work and the whole place completely gutted – it’s going to take up to two years to rebuild it.
“Right at the start, it was particularly hard because I had 30 staff working there whose wages I had to continue to pay.
“I also set up a charity [Street Kids Rescue] three years ago to look after disabled, orphaned and abandoned children in south-east Asia and quite a large part of that funding comes from the business.
“When I saw my store burning, I thought, how am I going to get the money to keep 4,000 children fed?”
The fire caused more than £800,000 worth of damage to the fancy dress and party shop.
Trevor Reeves, 56, whose burning furniture store came to symbolise the violence of the London disorder, said his losses at the 144-year-old family business were currently between £50,000 and £100,000.
Furniture is now being stocked at the next-door premises, where House of Reeves originally housed the side of his business which sold beds.
“We are not fully back up and running. The store that was burnt down still doesn’t exist,” he said, adding that restoring the building could take two years, or longer.”