There are many restaurants and other venues that could do it for that price. It depends a lot, though, on the time and day, as well as the kind of setup you need. If it is in the evening, seated, with a presenter, then there are somewhat fewer venues. Another factor is whether you can talk to the staff in Japanese. If you can only handle negotiations in English, the number of venues becomes limited. I haven't done an event at the Sunny Store&Cafe yet, but I know a couple of the staff there and am planning to do an event there sometime.
I know another venue that is a good one for events. It is in Akihabara. It is primarily a photo studio that has cosplay facilities. They also rent out the space for events - usually for photo shoots. The prices are incredibly cheap. The studio is big, so they often host parties with up to 100 or so people attending. The price for the studio on a weekday is less than ¥25,000 for 3 hours.
There are a great many venues, but you might want to check these out.