Mrs. Crawford is only interested in material wealth, whereas Mr. Shiftlet is not interested in money.
At the beginning of the story, the old woman and her daughter are sitting on the porch. Mrs. Crawford apparently does not think her daughter can get a husband on her own, since she is mute. She therefore seems to offer her daughter up to any stranger that comes by.
Mrs. Crawford wants Mr. Shiftlet to stick around, but he’s not interested in money.
"Lady," he said in a firm nasal voice, "I'd give a fortune to live where I could see me a sun do that every evening."
As he stays there, Mrs. Crawford tries to convince him why her daughter would make a good wife. She says she loves her daughter, but her descriptions seem purely selfish.
“…I wouldn't give her up for nothing on earth. She's smart too. She can sweep the floor, cook, wash, feed the chickens, and hoe. I wouldn't give her up for a casket of jewels."
She is clearly trying to tempt Mr. Shiftlet. When she offers him money, it works. They drive into town in the car he has fixed up, now less interested in the non-material apparently, and Mrs. Crawford gets her way.
Mr. Shiftlet may not be the best person in the world, but he still acts more morally than Mrs. Crawford. All she seems to care about is marrying her daughter, even willing to pay someone to take her.