What's strange in it? This deal has been offered by Pizza hut for more than 10 years. I remember having it 1st time in 1998. It was a great deal back then when I guess the deal was only for 250.
Considering the price, it's not really a big deal to offer unlimited pizzas. Because realistically how many can you eat in a go within 2 hours (the deal ends at 9 pm)? One large pizza? That's roughly 700 Rs. If you can eat more than 1 large pizza, then there are high chances that you are not doing to please your taste buds but just eating for the heck of it. Also the deal is available for only some of the pizzas (3-4 varieties)
Even if you manage to somehow eat 3 pizzas, the bottom-line remains that you spent 700 Rs for one time meal. In other times you can go to Lal Qila (and other Buffet restaurants) and have a variety of food items in 750.