I believe that this could be due to operator skill. I saw a boat being soda blasted at the yard I am at and the result was very good - needed a power wash, fill and fair a few low spots and barrier coat. The whole thing down to the last bottom paint done in one weekend....Soda blast - big production. Need to get yard's permission. leaves the boat bottom in devastated condition. Any epoxy/paint work subsequent would need extensive sanding to prepare. There is a theory about not being able to control depth of medium ingress, leaving pin-holes for water/osmosis issues - Epoxy barrier coat negates that, I think. This took an afternoon, and my buddy stood around with a beer in his hand. (I started sanding the bottom of my boat in January, every Saturday for 2 hours. He called a guy, and accomplished the same thing in 4 hours.) cost about $700 for a 30-footer.
The price you mentioned is about right for our region and that is what I was quoted.
...I was planning to sand the bottom, etc. - I totally changed my mind.