Charlie Hunnam is reminiscing over his choice to step away from "50 Shades Of Grey" ... saying the decision to leave it behind also probably means he left a lot of cash on the table.

We caught up with the actor at LAX Friday, and when asked about any regrets over walking away from the coveted role of Christian Grey over scheduling conflicts -- something he famously did at the time -- CH actually humored us a bit with a telling response.

Check it out ... you can tell he gets asked about this all the time, but all these years later -- it sounds like he wishes he would've done it, 'cause it would've made for a real fat payday.

As we all know, Jamie Dornan took over the role, and while the film was panned -- it cleaned up at the box office ... and you can imagine JD got paid handsomely to take charge.

Funny enough ... we also asked Charlie if he's even seen the movie(s) yet -- and remarkably, he tells us he still hasn't ... even almost a decade after the whole saga. Based on what he says here ... it sounds like he just hasn't had the time ... but definitely wants to catch it.

You could argue he's finally making peace with it all -- especially since he once described letting go of '50' as destructive, heartbreaking, and the worst professional experience ever.

TBH, if it's any consolation for Charlie ... it looks like Jamie didn't have it all that good starring in the movie 'cause he recently admitted he hid out in the countryside after feeling ridiculed over poor reviews for it/his performance.

Despite hate from critics, 'Fifty Shades' was a financial hit -- and it sounds like Charlie wishes he would've been able to get a piece of that. Hey man, you still got "Sons of Anarchy."

Speaking of which ... he's got thoughts on Dr. Dre almost being in it. If only, if only!