You are making a HUGE mistake, and mischarterisation, of the Hbf area of Frankfurt. It is specifically the "Bahnhof Viertel" RLD area, which is two blocks away in one direction from the station itself, that is seedy and the subject of these "bad/scary reviews" and only this specfic two block stretch. Go out of either the North or South Entrance to the station, however, and you will be presented with a completely benign urban enviornment featuring some of the best Hotel deals to be had in town. For example, diagonally out of the North Entrance of the station is the 4-star Savoy hotel, which offers weekend deals of as low as 42E/night! Or the Excelsior right across the N Entrance, 52E/night. So don't exaggerate the seediness, or you will miss out on the easiest and best place to stay in town...
Soulmate