If the builder had been honest and upfront then perhaps Kai would be more likely to accept budget overrun. However, trust has clearly been lost.
The flip side is that the industry is full of cowboys and dodgy people, so you sort of have to accept it to some degree. It's par for the course, if he was a better professional perhaps the original quote might have been double the price.
I fully agree with this statement. If we encountered issues along the way and it was made clear upfront that these were outside the scope and would incur an additional cost of £"X" if you wanted them addressed, then we could have proceeded accordingly. Not complete it' then say oh' that thing i did 6 months ago - you now owe this. i.e. an example he provided was toothing in brickwork from the old to new extension work ( i didnt request this) ; he apparently did not factor in the quote for this as it took 1/2 day more but the brick-layers went ahead and done it as they considered it the correct way and the proper way to finish tie in.
One professional did quote more than double the price we went with' but we also did not settle for the cheapest and actually went mid-range with someone who provided a solid reference.