Last year, Frijns combined the Sauber reserve role with an on-again, off-again GP2 campaign, but ultimately he lost both seats due to the money issue.
For 2014, he has been signed by Caterham and will appear in the green car at grands prix on some Friday mornings, but he will not combine the seat with GP2 because the grid of the support series is now dominated by 'pay drivers'.
And Frijns said F1 is heading the same way.
Referring to his situation in 2013, he admitted: "I thought it was not fair, as I had worked so hard for years, winning championships, going to the limit in every race -- but for what?
"This world is not fair -- it's about money. It's like you pay $20 million to the Barcelona (football) team and they put you on the field.
"It's the same here," Frijns told Spain's El Confidencial. "I'm not saying they're bad drivers," he added hastily.
"It has always been about money, but not as much as now. The crisis began four years ago and the teams are really suffering. And with the changes with the V6 this year, it's costing even more."
Explaining how his Sauber adventure ended mid-season, Frijns said: "At the end of the year the car was very good, but in the middle the team had financial problems that everybody knows about.
"Then came the story with Sirotkin ... I couldn't be in the car. But I don't regret the experience with Sauber, I know what the circumstances were and I can't blame them for anything," he insisted.
Now, he has started a new adventure with Caterham, and he has already tested the 2014 car at Jerez, albeit amid Renault's technical crisis.
"I changed my manager and I got this opportunity with Caterham," he said.
"I am more involved in the team than I was (at Sauber) last year, I have more time on the track, which is quite rare these days.
"I feel that they believe in me, and that is very important," added Frijns.