Saying you have received an estimate tells nothing about the estimates content or the size of the coverage.

I'm sorry snooyb.
Here's the complete estimate:

Front Irrigation
Install new valve and run new sprinkler line to feed front grass. System will consist of plastic valve and schedule 40 pvc supply line to feed three inch pop-up Toro
sprinklers. Total of 10 sprinklers to water front lawn.
$470.00

Timer Install
Install new irrigation timer on garage. Run sprinkler wire from valve to new timer.
$425.00

A decent timer would be in the range of $40-60. The $425 could be high or not depending on what's involved in installing it. How far is the valve from the controller? Will the wiring be run through pipe in a trench, or just laid directly in the ground? What's involved in getting power to the timer?

If you wanted to save money, installing these systems is incredibly simple. For under $300 you could buy all the irrigation system parts and rent a trencher.

The wiring will just be laid in the ground. I'm not sure
what's involved in installing it -- I'd better ask the contractor.
Unfortunately, I'm not enough of a DIY person to consider it myself. :)

"Total of 10 sprinklers to water front lawn. "

You can't ruin that many sprinklers on one valve! Needs two valves and two runs.

Get a second and third bid.
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Also, the bid should specify brand and model number of the controller and valves.

Thank you, lazygardens.

This is actually my third bid -- and the other two only
used one valve as well.

I had asked this company for more info before I saw
your post. Here's what they said (the two valves I think
refers to my parkway, where I'm keeping the existing sprinklers and want to hook them up to the new timer):

"I priced you on plastic Rainbird valves as it states on the estimate for $120 each. The timer is an Irritrol R-series which will be placed next to the power outlet near your garage door. The timer is simply plugged to the closest power source. Irritrol company offers a 5 year warranty on their products. The wire will run under your house, in thru the vent near the valves and out the vent near your chimney. A small hole will have to be drilled to your garage wall to pass the wire through. Price includes connecting new two valves. I am not sure how far the valves are from the controller but it will be about 60 line feet.

In comparison with your other bids information it is very similar, we will use 3" Toro pop-up sprinklers with standard nozzles, align and adjusted. The pipe will be 3/4 schedule 40 pvc pipe buried at 8 inches. Controlled with plastic 3/4 rainbird valved and an Irritrol R-series controller."

What do you think? Also, is it important that a company
be licensed to do this job? Thanks!