You probably went to the Toyota dealer in which case they’re going to talk you into replacing a bunch of other things in addition to the timing belt.
The belt itself is cheap. You can probably get a good one for $20 unless you go through Toyota, then you’ll pay a lot more. A mechanic could change the timing belt in 3 hours. Find out your mechanic’s hourly labor rate. If you shop around, you could have a new timing belt installed for $300.
BUT, at 100,000 miles, I’m guessing there are other maintenance items that should be done in addition to the timing belt.