I'm not sure about Ethel's reasoning regarding low wages. Here in Suffolk we have some of the lowest wages in the country but plenty of areas where house prices are very high. (A simple beach hut, in Southwold, sold for �90,000 this week!) ;-)
House prices tend to be high in those areas which are within commuting range of major centres of employment (particularly London). Lincolnshire isn't really close to anywhere.
Prices are also high around areas of outstanding natural beauty. Lincolnshire is largely drab and flat, with hardly a tree in sight. The coast doesn't have the natural beauty of counties like Devon or Cornwall, or the man-made delights of coastal cities like Brighton.
Lincolnshire's economy has historically depended upon the agriculture. The mechanisation of the industry means that there are now very few employment opportunities within agriculture. In some counties (e.g. Suffolk) jobs in agriculture have been replaced by jobs in service industries (e.g, insurance) but Lincolnshire is too far from the capital for major firms to consider relocating there. (Employers relocating can boost house prices in some areas. e.g. house prices in Sheffield shot up when the Manpower Services Commission relocated from London. Lincolnshire can't attract many major employers).
Chris