The majority of Great Rail Journeys customers believe the cost of Covid tests to travel abroad should be under £50.
And more than half of those asked think the price should be less than £25.
The operator fears the loss of a quarter of all its bookings due to the cost of having to pay for tests.
Chief executive Peter Liney said: “It is imperative that tests are both affordable and easily available to build consumer confidence.
“It is concerning to see that the current testing proposals represent a significant cost for passengers that will be a real barrier to the return of long-awaited holidays.
“Our research tells us the current cost of PCR testing is ‘unreasonable’ to holidaymakers and will need to reduce significantly to be considered viable – 81% of our customers believe under £50 is a reasonable price to pay, with 52% actually thinking the cost should be under £25. Just 1% consider the current cost to be appropriate.
“We predict we could see a loss of 25% of bookings just as a result of customers having to pay anything at all for testing.”
He added that many questions remain unanswered as to how and when international travel can safely resume from the UK.
“We, along with the rest of the travel industry, urge the government to provide more clarity and to ensure the proposed traffic light system and travel testing regime can work effectively,” Liney said.
“Our customers keenly await their booked holidays, and it is important they are provided with reassurance that the right steps are in place ahead of travelling again.
“Ninety five per cent of our over 60s holidaymakers are not at all confident about travelling to amber countries, so understanding which countries will be on the green list is key to unlocking travel.
“Our research indicates there is appetite to self-isolate on return from an overseas trip, and this may provide a reasonable alternative alongside free-of-charge lateral flow testing, reserving the use of gold standard PCR testing for instances when a lateral flow test is positive.
“We look forward to helping our guests enjoy their long-awaited rail adventures, but, despite being more than a year on from the start of lockdown, it is highly disappointing that so much remains unknown about the government’s roadmap for overseas travel.”