Nothing, I wouldn’t want someone who places so little value on my work as a customer.
Remember Whatsapp used to charge a dollar. Multiply $1 by how many millions of users. That's not bad assuming a profit margin is there.
It might be irrational but people value what they buy by how much they spend. I remember when I left my last full time job I felt we were undercharging our customers. I went back to those same customers doing the same work and charged them three times as much as they had been paying. Their attitude towards me changed completely, I was really shocked at the difference, I'd gone from being a grunt who installed systems to a valued member of the team.