I'm A Celebrity... Get Me Out Of Here has brought in over £1m to Wales' economy, say the owners of the castle hosting the reality TV show.
This year's series, which finishes on Friday, is being filmed at Gwrych Castle, near Abergele, Conwy.
The castle's trust insisted local firms were employed as part of the deal to use the Grade I listed building.
One local coach company said the work had been a "lifeline" during the coronavirus pandemic.
TV presenter Vernon Kay, author and podcast presenter Giovanna Fletcher and radio DJ Jordan North are in Friday night's final after Eastenders actor Shane Richie was voted out on Thursday night.
Mark Baker, chairman of the Gwrych Castle Preservation Trust, said ITV has fulfilled its promise to use local contractors wherever possible.
This included builders working on the set and firms providing portable toilet and temporary road surfacing, as well as accommodation for the crew.
"The programme is one of the biggest TV productions in Europe, and that's been reflected in the number of people on site and the amount of money that's been spent in the area," said Mr Baker.
"Local companies have supplied everything from the t-shirts the celebrities are wearing to the bags of castle coins that they win in their daily challenges.
"All in all, we've counted up to 50 Welsh businesses involved just in getting the castle ready for filming."
'It's really exciting'
Liz Castro runs Place2Print in Llandudno, and printed the t-shirts, clothing and accessories worn by the celebrity contestants.
The timing could not have been better, having been forced to close earlier in the year due to the pandemic.
"It's really exciting. We watch the programme at home each year but for ITV to contact me was a major deal," she said.
"It's been really good to have a big job come through the door after being closed earlier this year.
"It's been a hectic few weeks, but we've been working with an amazing bunch of people.
"We had to move fast and get everything ready at speed when the names of the celebrities were confirmed.
"People may not realise, but all the celebrities have name tags in their sleeping bags and on their water bottles, so they know which is theirs. We printed them all.
A few miles away from Gwrych Castle, Voel Coaches has described the programme as a "lifeline".
The company had seen its business wiped out by the pandemic but said this contract, transporting staff and crew both to and around the castle site, has safeguarded its immediate future.
Chris Gentile, marketing manager said: "Since the coronavirus pandemic, we've had a really tough year.
"We run excursions and holidays and our business was almost non-existent after March. We suddenly found ourselves having to refund everyone.
"But in the last few months, we've been able to create jobs and take on new staff. It is still tough, but this work means we will get through.
"When people realised that we had the contract, we had around 150 to 200 phone calls from people who wanted to be drivers with us."
Welsh language interest
From Ant and Dec welcoming viewers every night with "noswaith dda" - good evening in Welsh - to Kiosk Cledwyn and his Yr Hen Siop - or Ye Old Shop - the Welsh language has had exposure around the UK.
An average audience of 10.9 million watched the first show on 15 November and people offering Welsh lessons say they have seen an increase in interest.
"I've spoken to many Welsh language lesson providers and many have told me that they've seen an increase in traffic," said Garffild Lewis, the language consultant who worked with ITV on the show.
"We introduced the language in a subtle way. It's not out there shouting at you but we've introduced words here and there and the language can be seen round the set".
"That has brought a presence and it's had a very positive reaction.
"The profile of the language has increased and that leads people to wanting to know more and learning it, which of course is very important".