Mike:
I think you may need to consider some additional needs that will/could in turn result in more costs. Such as, does the bunker, greenside or FW have drainage? Doubtful, and if it did, it should probably be replaced, so this will need to be added. How far would the exit tile from the bunker have to run to connect with a main drain line on the course, or to day light to an out of play area?
A. Remove sod, old sand and soil & excavate to depth required ( I presume it is close the depth that the club wants and only minimal cleaning is needed).
B. Add new underdrainage (HDPE pipe smooth interior wall, fill trench with gravel or sand. Includes installation of an exit tile - let's assume 150 LF is needed.
C. I presume no liner is needed, so compact the floor of the bunker and cut the edge to size and shape desired.
D. Install sand- the act of doing so is fairly cheap, but the product costs can be all over the place..from as little as maybe $8-$10/Ton for a local product to $75/TON for some of the processed 'high performance' bunker sands on the market. This is a very subjective component to each club, though testing labs and the USGA are constantly trying to make it more objective based on a complicated set of parameters.
E. There may be some resodding around the edge when done
So for a 2,500 SF bunker using the outline above and using 4-5" of sand with an average cost of say $40/TON, you could expect to see total costs to range between $4,000-$5,500.
This could shift up or down a fair amount depending on amount of underdrainage, exit tile and type/quality of sand used.
Building a new bunker--here again it depends on the site conditions, such as is it condusive for a bunker? is there much excavation needed? If the cut is fairly clean and the area of disturbance can be kept contained, then sodding will be cheaper. How much exit tile needed? I presume you are speaking about a new bunker around the same 2,500 SF size?
So, following the same basic components above and knowing that you will need to remove several trucks, or many dump trailers of soil and use a fair amount sod to finish it off you could spend between $8,000-$10,000.
Once again, these could swing up or down easily depending on amount of soil to remove, drainage and quality of sand used.
A 2,500 SF bunker is a fairly big bunker, but for Langford and Moreau it fits the scale they often used.
Good luck with this