Even the core texts are extreme. The law of Moses all the GOP know by heart is the one about men laying with men. They talk a lot less about the laws concerning the sale of your 12 year old daughter. Both the buyer and seller are protected. If for some reason the buyer finds the product not to his liking, he can return it for a refund. But he can't expect to get a total refund because like a new car, her resale value goes down as soon as you drive it off the lot, so to speak. So they are both protected by these laws.
God is love.
A side note. You could sale any of your kids into slavery, or as a bride. The only difference would be if a girl was sold as a slave, she was a chattel slave, meaning all her kids, etc, etc would always be slaves. But if sold as a bride, it would be up to her husband to decide her children's fate.