Love the 'Butterfly Effect' :D
one small story that I still laugh at today:
I wanted to get a new cell-phone contract and pay for it with my credit-card. My credit-card has my middle initial on it and validates against the full name. The phone company, for whom I'd been building interfaces a couple of years prior to that, did have middle name in the application form, but the interfaces we built did not transfer that field from the frontend form to the backend system. Result: my phone contract was denied, as my credit-card refused validation.
Even though I tried to explain this to the embarrassed sales-person there was nothing he could do about it. I effectively sabotaged myself by implementing that interface even though I knew about the resulting issues. I've had similar smaller issues-and-effects over the years with many of my retail or logistics customers, but nothing as directly blatant as this.
As Steve pointed out it goes much deeper than that: there's an untangible side to this. The more defective interfaces I implement, and the more I get paid for implementing defective systems, the less that money it worth. I've noticed an actual decrease of worth over the years I'm getting in return for the money I earned. Which is logical of course: I'm creating less value for the money I earn, so I get less value in return when I spend it. As my customers are not willing to implement better interfaces I have to increase my rates to be able to buy the intended value with the money earned.
So building lousy interfaces is not just directly, but also indirectly, more expensive than building good systems.
Alas I'm also just a HomoSaSa and my excuse is: I don't really care much about those systems if the customer is not interested enough to change his architecture. I just live with the fallout. That's why I chose IT: my heart is not in it. If I'd chosen literature, art, trekking, sailing, helicopter piloting, or any of the other things I enjoy (or intend to enjoy in the not so distant future), I'd face a very real problem of compromising my creativity, my enjoyment, my vision of my future what little is left of that vision.
With IT I just have a good laugh at the lunacy in that business :D