Without knowing exactly what is getting fitted and seeing the job it might be a good price. I take it that the spark will run in the cable, drill through any walls in the way, fit distribution board in the shed, connect up cable in house and fit rcd, fit all sockets and lights in shed and wire them. Fully test installation and provide you with test cetificates. How is cable being run from house to shed? Digging trench? All in a good days work so price might be ok.