Are some projects ruined by deadlines ?

Yes some projects can be ruined by inappropriate deadlines. But once you see the deadline and see it you have to go with it. The person who agreed to the deadline is depending on you to deliver the goods but if you don't think the project is viable with "gold-plated" components then it up to you to state your feelings on the matter as early as possible. At least that way you have should have it on record and that you are doing it under protest.