I have never done a timing belt on a Toyota tundra but have done one on a Subaru and know that a few things can change the price by a large amount. I would recommend changing the tining belt idlers as well as the water pump if driven by the timing belt that could be the reason for the differance in price.
Like I said I have never done a Tundra but just wanted to give you somethings to think about.
Hope it helps
I just had my timing belt done at 95000 mi. The timing belt was like new but the water pump was leaking. Had the job done for 800 and brand new antifreeze. These trucks will run over 300000 mi if matained