I haven't been to Paris in recent decades, but this summer I spent a lot of time in Brussels and Amsterdam as well as in smaller cities in Belgium and the Netherlands. I was also in Lille (France) and some nearby cities for about two weeks. I think Tocard's price warning is spot-on. My meals, including those in Asian and Middle Eastern restaurants, often exceeded 30 euros by a considerable margin, and I wasn't ordering the menus' expensive options. Most of the time I ended up paying for bottled water, which is an annoying (to an American) extra expense of 4 or 5 euros; a large bottle shared with others would have saved money.
French restaurants often have weekday deals at lunch time that are considerably less expensive than ordering a la carte. I struggle to break free of my sightseeing activities long enough to sit down to lunch, so I totally understand why you're focusing on dinner as the time for a nice group meal. However, if you can manage to get your main meal at lunchtime once or twice (probably needs to be on weekdays), that will help your budget. Alternatively, a couple of dinner-time meals not eaten at full-service, sit-down restaurants will help. Creperies and pizzerias will probably be less expensive. Be careful about ordering desserts in restaurants, though; they'll probably cost at least 8 euros. A selection from a patisserie should be less expensive.