We loved T-Rex for the atmosphere and effects for our two boys - but I would say it was easily the most expensive meal of our trip (Although we had eaten at Le Cellier on the dining plan so didn't really look at the cost for that, but would guess it is comparable) - but to give you an idea - for 2 adults (starters and main), 2 kids meals for a 3 yo and 6 yo and a shared dessert (the volcano) it was over £100 with only soft drinks.
I wouldn't say the quality of the food was any better than the cheaper offsite restaurants, but we would do it again purely because we are on vacation and you are paying for the overall 'experience' not just the food - but then we also really enjoy the Rainforest Cafe and the food is not anything special there either.
We enjoyed T-Rex but had an early lunch there so it was very quiet. I remember there being so much food that they asked us if we wanted to take some away in a box
4 adults we all had mains and shared the chocolate extinction and were $130 before discount.
Would definitely go back (& will request to sit in the Ice Cave next time) definitely call ahead and book though. Was an hour wait for those who didn't. We rang the day before and had about a 10 minute wait.
Booked for Lunch Time 1.30pm, will be on the day when we are going to the park on the afternoon/evening instead of the day, also i saw a few reviews which said T-Rex can be hell on night time as it gets so busy....