That's bleedin awful....
I remember various discussions, before the BB kit price was announced, considering the option of custom pistons, boring the barrels and nicasil plating. Last chat we had with Chris Bushell we worked out a price of about £350 (£100/piston, £60/barrel boring & coating, £30 for gudgeon pins etc)
Don't know if that's realistic as I haven't done it for years, but might be worth a try talking to those that can be more accurate.
Good luck and keep us informed. Use of 900 engines is not an option!!
Cheers,
Ali