> You call a contractor and tell them everything you want done and then ask for an estimate and they tell you, "I don't know. It'll cost what it costs. Every project is different and I won't know until I'm done."

I see you haven't needed to hire many building contractors. "I won't know until I'm done" wasn't how the engagements started, but it's how they all ended up. When the budget's gone and they're only halfway done what are you gonna do, live with a hole in the wall and no running water? If you got a home renovation done on time or on budget (I refuse to believe both), congrats on catching a unicorn.