here is a short list of hotels in the center of Rome. The price for a double room is between $ 100 and $ 150, and I have been inside of all of them (excepted for the Mimosa and Jonella) so I can say they are ok.

Ciao Flavio in Rome

Hotel Abruzzi, piazza della Rotonda 69, tel. 06-679-2021. Hotel Campo de' Fiori, via del Biscione 6, tel. 06-687-4886. Hotel Sole, via del Biscione 76, tel. 06-6880-6873. Hotel Pomezia, via dei Chiavari 12, tel. 06-686-1371. Hotel Piccolo, via dei Chiavari 32, tel. 06-689-2330. Hotel Smeraldo, via dei Chiodaroli 9, tel. 06-687-5929 Hotel Lunetta, piazza del Paradiso 68, tel. 06-686-1080. Hotel Mimosa, via Santa Chiara 61, tel. 06-6880-1753. Pensione Navona, via dei Sediari 8, tel. 06-686-4203. Pensione Panda, via della Croce 35, tel. 06-678-0179. Pensione Jonella, via della Croce 41, tel. 06-679-7966.