It depends on the size and type of extension. Small porches or flat roof extensions are very reasonably priced. More substantial two storey extensions can be expensive. In general, the price is roughly proportional to the amount of space you add to your home.
Marazion
Marazion is a civil parish and also town, on the coast of Mount's Bay in Cornwall, England, UK. It is 2 miles (3.2 kilometres) eastern of Penzance as well as the tidal island of St Michael's Mount is half-a-mile offshore. At low tide an embankment links it to the community and at high water guest boats lug site visitors in between Marazion as well as St Michael's Mount. Marazion is a thriving vacationer resort with an active area of musicians that produce and offer paintings as well as ceramic in the community's art galleries. Marazion exists within the Cornwall Area of Outstanding Natural Beauty (AONB). Virtually a 3rd of Cornwall has AONB classification, with the same standing and protection as a National forest. On the western side of the town is Marazion Marsh, a RSPB get as well as a Site of Special Scientific Interest (SSSI).