First of all I appreciate you even thinking about the ethics of purchasing an animal, that’s really great.
You having a single pair of breeding geckos is honestly not going to make that much of a difference. In order to have any effect you would need to produce and sell hundreds of geckos a year and that simply is not possible.
Should you purchase this animal anyway? I guess it depends how you look at it. It is a captive bred animal and so you are telling the breeder that there is a market for this and so hopefully more will be produced. All reptile lines began as wild caught individuals so it’s difficult to condemn someone for purchasing first generation captive born animal. When there are more CBB animals available on the market and people purchase them eventually importing WC animals will stop.
To make a long story short, you as a single individual do not have that much control on the industry unfortunately. Regardless of your choice hundreds of other people will make their own choices. I think buying CB animals is a great start and you will have healthier pets in the long run.
I might be naive, but I think he would be making a difference. If you’re loud about the fact that you’re one of the few breeders of a commonly imported species, I think people will start purchasing CBB animals and maybe the trend will spread. If you think you can make a difference, DO IT!!! Be loud! Be proud! Tell everyone everywhere that you’re breeding them!