@oxyhyxo exactly, I agree with every single word you've written. When the standard of work drops, so does the quality of the relationship. I believe this also stems from the fact that those in extreme need of earning something may resort to unprofessional situations like this and consequently accept compromises on payments.
Over the past 20 years, I've learned that insisting on delivering quality work is necessary for peace of mind. Sometimes I've lowered my compensation to allow clients to achieve better results if there were (real) budget constraints, and this has generally been a good long-term investment.
I often work with developers. Some of them I've known since they were very young and have changed jobs several times. A great satisfaction is when, years later, they call me to propose working together in their new company.
"You're going to reap just what you sow."
@stefano additionally, so much of my work has come from clients who had been burned by other consultants who liked to cut corners/oversell/underdeliver. A lot of IT providers feel pressured to cut their own throats to attract/retain customers and this is exactly the wrong path (in fact, it was often part of my pitch - this is what it costs for me to provide this solution/service sustainably. If I go broke or constantly have to constantly churn and retrain staff to keep the lights on its a negative for both of us)