Entirely up to you and what you feel comfortable with. A warranty is only as good as the company providing it and of course you ask what if the locksmith is not around in 10 yrs but also what if Emtek is not around? I doubt they are going anywhere but you never can tell. You right though the odds are you will have no trouble with the locks and never need the warranty but there is always the what if?

Like you, I don't understand the difference in pricing between lock sets. He's basically charging you for labor and whether it's fair is difficult to say since rates vary by location.
Call another locksmith for a second estimate and also call a local handyman and ask his labor costs.

Why do you need a locksmith? The only real specialty he possesses is changing the keying of the lock cylinder. Any handyman can install a lockset into an existing door. If you brought 3 locksets to his shop, and asked him to make the keys all match, he'd do the work for about $50. Your handyman can install all of them in a few hours, maybe $100.

$100 for a few hours of handyman work? Wow. I need to live where you do (our prices are about 3x that).

I agree with the others in principle though. Buy Matched Locks from Emtek online, then have someone install them for you--a handyman, your DH, a friend, you. You won't need to pay to have them rekeyed if you buy them matched to start with. When I bought my (Schlage) knobs online, the online company made sure they all were keyed the same.

The locksmith is just trying to make a living. If you are so concerned about cost why not have the sets keyed as you like and then install them yourself?

You should buy an extra lock set so you will be able to lock your house while a replacement unit is being shipped from Emtek.

Emtek has only been making hardware for about 30 years; Baldwin has been doing it for 60 years.

My Schlage entrance hardware has failed twice so I now have a Baldwin set.

I purchased new door hardware for each interior door in our house when we moved in here in 2005, as both my father-in-law and I had arthritis and difficulty with turning knobs. I changed our doors to lever hardware. One has failed. I went back to Lowes to get a replacement, and the styles have changed. I have not contacted Kwickset, I am not sure it is worth it to try and find replacements for these super-cheap doorknobs.

Maybe the knob styles don't vary as much as the lever styles do, but I would not trust that any particular style or model is going to be available for more than a few years. Just as Renovator8 gets a replacement set for his exterior door, I would suggest getting an extra interior door set. Having the "insurance" of a free replacement won't help you if the models have changed in the meanwhile.

Since you are replacing existing door knobs, try doing it yourself. The hardest part is getting your tools together and opening the packaging. Pull up a video on You Tube. It really is an easy job.

I bought an Anderson 2500 or 3000 a year ago from Home Depot for around
$300. My first thought was to buy a cheapo $99 door because its the back
door, but after listening to my local Locksmith's advice and seeing the features of the Anderson (top glass slides
down to reveal bug screen) and their 45 minute install, I was sold. TheLocksmith adviced me not to buy cheapo $99 door because it doesn't lasts for a longer period and need to be replaced soon. Then,I got the door up by myself in less than an hour and looks/works great! Best money spent on a door! Some locksmiths are really honest.