>>84338473You should look for areas on the east end of the city! Sure, this is farther from "fun" areas like Shinjuku and Shibuya, but you can find good hotel rooms for as low as ¥6500 a night (like $46 USD) and lower if you're okay with capsules and more bulk accommodations. Being close to a train or subway is most important! Not only that, but you'd be a little closer to the Makuhari Messe location, which is about 65m away by train.
Plus the east side has Asakusa with classic temples and buildings, Chiyoda and Ginza with fancy bars including the Choya bar, and Odaiba with the Gundam store and statue!