Budget vs actual cost

Recently, I have been asked to bid on  custom homes with the buyers giving me their specific budgets. They had already contracted a designer to produce the plans. I was shocked that the designer had no consideration for the clients budget. Although they designed a beautiful new custom home; it was at least $75,000.00 over their budgets. Not only was they client horribly disappointed, I was as well considering the time it takes to accurately price a custom home.