Example of low ball estimates. See my truck, the color is white. I was quoted $1500 for the paint job back in the 80s. What I negotiated. Painted inside out. All trim holes brazed. All dents lead filled. I got everything... eeee haw. Then the next day the owner of the shop called me and told. Me, "we don't lead fill, we're not brazing the holes, nor can we fill any holes with anything or paint the interior for that price. So, I negotiated with him and only caved on brazing and lead filling. He painted the truck inside out and pulled and filled dents and holes with bondo. Yes he lost money. But kept his shops good name. The guy who wrote the estimate got fired. And I always feel kind of bad about that paint job!
So, apply that to any cheap estimate. Something has to give. Not an engine, but I like telling that story!
j