Different cars have different layouts.
For Example, (from my own experiences) I can change out a Timing belt on a 2.3L Ford in about 15 minutes, (Had to do it on the side of the road once!) Honda Civic (80's Model) took me about an hour, Small Block Chevy (chain & gear) about 2 hours total time
On a Cadillac Catera, it's somewhat more complicated, what with dual OH Cams, need to remove a lot if "crap" just to get to the cover, remove the Harmonic Balancer, use a special tool to keep all the cogs aligned, very complicated, and it takes me about 5-6 hours, give or take.
(Some Camrys have the same type Engine, 3.0, 3.2(?), IIRC, personally, I wouldn't even think about doing it for less than $800.00).
Oh, and as far as your parts cost breakdown, you cannot just count the Timing Belt alone, there are seals, pulleys, and most importantly the Tensioner that should all be changed at the same time. (Tensioner failure is as common as belt failure in most vehicles)