Bath is an expensive city to buy/rent in. But once you've got past that hurdle its no more expensive than any other city in the south of england. Ok so things like council tax are high - but students dont pay council tax anyway. Plus you get to live in one of the most beautiful cities in england, not far from one of the largest cities (bristol), some of the most stunning countryside (mendips, exmoor, dartmoor, cotswolds), and in a city with good transport links to the rest of the country.
The on campus accommodation, as much as we might moan about it, is probably among the highest quality around (especially solsbury and marlborough) and being a small city, "home" will never be too far from campus even in the 2nd year upwards. Being a tourist city there are plenty of jobs around, especially if you want to stay in bath over the summer season.
So yes, Bath is expensive, but its definately, 100%, worth it.