Also, even for a suit, "Maintainability is only a concern once lack of such starts impacting your actual customers." is only true if by "actual customers" you mean shareholders. If you really want to get down to it and make an obnoxious out of place point, you can technically fuck over the customers all you want so long as doing so does not actually hurt the business (meaning: hurt the shareholders). Bonus points for figuring out how this could be done by a consulting company.
A typical example is, "If we don't get something out the door, we'll be out of business. 'Shit' is something that can be shipped quickly, therefore we must ship 'shit'."
But companies that ship 'shit' generally go out of business anyway. Either their customers find it unappealing and leave, or ongoing maintenance quickly becomes so difficult and expensive that the product can not improve except by being rewritten under new management.
With something like a secure website (or script injected into arbitrary websites by a large ISP) the severity of the security vulnerabilities that tend to result from "shipping shit" often you only get one or two chances as a company.