This sounds a bit on the steep side alright, a good kerber would do around 200m in about a week concrete backing and all. And working out at a rate of about €30 - €35 an hour working 9 hour days from 8 to 6 and an hour for lunch. It should cost you about at the maximum €1200 - €1600 labour only. With kerbs only about €3 -€4 each costing around €800, one load of leanmix for bedding costing around €400 - €500 and two loads of concrete for the backing around €1000. He'll cost you almost as much as the material, ask him to re-quote you, if you will lay out the kerbs for him to place them, teleporter for a days hire you'd have it done in no time.