The latest price increase sees the cost of using the loo in Central Station increase from 30p to 40p.
And the rise makes the transport hub the most expensive station toilet in Scotland.
Although the lavatories have had a recent upgrade, passengers were unimpressed by the price hike.
Laura Robertson, who popped in to use the facilities with her daughter Erin, 9, said: "In Edinburgh the toilet is free for children but I had to pay for Erin to use the loo here.
"The facilities aren't bad but they're pretty cramped and I've seen a male attendant come into the ladies' twice without any warning.
"I'd rather they used a female attendant."
Stacey Silver, 28, is a regular commuter and said the toilet upgrade made a difference - but still doesn't justify the price.
The office worker, from Parkhead, said: "The toilets do look a bit fresher now but for a third extra I'd want cloth hand towels and scented lotion to justify the price.
"There isn't even soap in a couple of the dispensers. Obviously 40p isn't a huge sum but a 33% increase is well above inflation."
A station spokesman said: "Glasgow Central is the busiest station in Scotland and, as a result, its facilities are heavily used, requiring constant staffing and maintenance.
"We have not imposed a price rise at our toilets for almost 10 years."