Everest offers a three course pre-theater menu for early diners at a significantly reduced price from a normal meal there.
As mentioned above, Elizabeth offers dynamic pricing and the prices fluctuate greatly. Some meals occasionally are as inexpensive as $35 per/person while other times pretty much the exact same meal goes for $175. Well worth monitoring Elizabeth's Facebook and/or Twitter account as sale prices are advertised via social media. Early seating on weeknights often is usually at a lower price than other days/times, but be on the look out for the drastically reduced special pricing.
Some Chicago restaurants offer good deals based on the day-of-the-week more so than time of the dinner; i.e. Simple Sundays at Embeya ($29 prix fixe), $5 specials at Table Donkey Stick on Mondays etc. - so if looking for good values, do not limit yourself to seeking out early bird deals.
Twitter: @Goof_2