Well, the main problem with that... people often put the exact same value on an animal, that they pay for it. Too often people who get a pet for free, see it as expendable. The purchase price of a pet is by far the cheapest part. If they can't afford to buy it, they can't afford to take care of it. Now, this is just statistics. I'm not saying it ALWAYS happens this way. You just have to be very careful when giving away 20 living beings, that you put on this earth, for free. I know I'd have a hard time worrying at night.
The sad reality of pets in general, not just bearded dragons. Is people buy them ill prepared for whats to come, pet stores don't have sufficient regulation to ensure people are entirely informed about every detail they need to know.
Take the two beardies my partner and I have for example; a 7mo Male and a 4mo female. What you don't know till you buy & start looking after them is; the real cost of food, the real cost of the viv+necessary equipment, the cost of bulb replacements every 6 months, the cost of supplements & medicines, the cost of an exotic vet should it become necessary. And they definately don't prepare you for learning how to see signs of indigestion/impaction (Crickets slightly too big or beardie was a bit of a pig) and other minor health issues if left unchecked would become major problems. Despite all of this and being ill prepared by pet stores, I absolutely love both the beardies we have. I'd do everything and anything to keep them in tip top health including sell a kidney or cornea if it came to it.
The hardest thing for a breeder who trully does breed for the love of the species, to better protect it and make aware those who wish to experience the joys of beardie ownership what they're getting themselves into, is to make sure the beardie they sell is treated correctly. So Ethical? Yes, of course if your doing it for all the right reasons. Is it possible to ensure ethical treatment of the beardies you sell? Nope, not until real regulation of the pet industry begins to exist.