welcome to the forum - great to have you on board.
Your kitchen maker's price seems OK to me (period style kitchen designer here) - there may be cheaper doors 'off the shelf but yours look like they may be custom.
So, a maker will have to source, inspect and buy suitable timber, machine it to suit the job, glue and fill the timber in preparation for making the bevelled panel inserts, then assemble the doors, sand them, then polish them .... all to precisely match what you already have .... that's no easy task.
Even if he finds doors from a supplier that are the same, he has to inspect and pay for them and then supply them to you.
If his price includes fitting the doors then I feel it is most reasonable, as he will have to come out, machine your existing housings to fit the hinges, then put the doors onto your cabinet and adjust them to ensure they fit. If you want matching pulls, he will supply and fit (or just fit) those. All of these things add up to several hours of work, plus the cost of the doors.
If I am understanding the project correctly, this will still leave a gap where the rangehood is - an alternative would be to replace the rangehood with a quality inbuilt one (or cover the existing rangehood) and make the entire overhead section look like cabinets.
....catchy phrase here