I kept a log of costs from the first ever season of DD back in 2005:
http://www.horrible.demon.co.uk/bikes/racing2005.htm If the check the table on the right of that page, you'll see each item costed, so just remove the stuff you don't need or want to include.
My rough cost to get a bike ready was £2500.80, but that included the cost of the bike (£1200), the ACU test, twin caliper conversion (new front forks, twin disks, calipers, etc) and so on.