What value? Hard to tell without knowing if there were any health issues in the last generations. Or what their genetic characters are, which is quite important to me. With random mixes, they are just rabbits. Not better or worse than any rabbit labeled "purebred" from a sketchy "rabbitry", but I reckon market value isn't about that. What they can be sold at depends a lot on where you are, and how the market situation is. I'm happy to get 15-20€ for a 5 month old rabbit. Which doesn't even remotly cover the work that went into this rabbit already, but there are some I'm quite happy to get rid of.
I sometimes sell a rabbit or the other, but I do not breed to sell. Mine are mixes too, and I only sell ones with outstanding characters and when I'm confident that they are free of health issues. Not much market there, rescues are filled to the brim with mixed rabbits, many from accidential litters available for free, but getting a rabbit from there at least normally includes a health check and often they are already spayed or neutered.
Not trying to discourage you from breeding them, just pointing out some things imo you are going to notice. Always have a Plan B. There's that saying "You shouldn't breed rabbits if you don't like the taste"