Brass-framed revolvers are cheaper because factories typically invest less effort into their fitting, polishing and finish. They are almost always inferior, in these regards, to their steel-framed counterparts.
Compare a brass-framed revolver to an identical steel-framed one. The price is lower because of the lesser quality. The strength of Colt vs. Remington revolvers, as applied to the steel-framed versions of good quality, is a moot point -- as long as we're talking black powder or Hodgdon Pyrodex P. Either will last decades with proper care. Black powder and Pyrodex P generate pressures amply handled by either design.
A problem emerged when Hodgdon 777 was introduced. It was designed to approximate black powder pressure levels with 15 percent less propellant. Unfortunately, too many shooters wrongly assumed that 777 was to be used equal-volume with black powder, like Pyrodex P. Not true.
Hodgdon does not recommend the use of 777 in brass-framed revolvers. Even in the 15 percent reduced charges. There's a reason: 777 is stout stuff, especially when mistakenly used in equal measure with black powder.
I've owned two brass-framed revolvers in more than 40 years of shooting cap and ball revolvers. Both were of poor quality and gave me problems. One wore out. With reduced loads, they're okay for beginners but should never be used with anything approaching a full load. Doing so will accelerate wear and cause damage.
I've long urged people to buy steel-framed cap and ball revolves, mostly because of the likelihood of better quality in a steel-framed gun. The steel-framed guns are stronger too, but this point is moot unless one plans to use Hodgdon 777. Both designs were amply strong long ago, for the black powder for which they were designed.