Price for close board fence and concrete posts

Just reading the comments above especially the "seems expensive if you are not in the business" one.!!! My dad ran a building firm and directly from school (1989) i worked for him for 2 years whilst doing a city and guilds brickwork course. When i recently built an extension on my house,(with a little help from my dad)i had spent �£1000 (planning etc)before i had even put a shovel in the ground to dig the foundations. When we had completed and decorated the cost had risen to approx �£3700. Cheap as chips!!! �£4000 for a �£20,000+ extension!!!!