When people call me about replacing a lock, inevitably we start talking prices. One of the variables I spend more time explaining is whether or not the door is prepped correctly. If a door is prepped for a modern tubular lock it must have a 2 and 1/8″ cross bore and a 1/8″ side bore.
In the old days people didn’t have access to inexpensive electric drills or were too cheap to buy the correct auger bit to drill 2 and 1/8″ holes. They reasoned, why don’t I use the 1/4″ bit I have and only drill out those holes that are strictly necessary? Sometimes they didn’t even drill holes, sometimes they chiseled the hole. The lock they bought at Home Depot requires a nice round 2 and 1/8″ hole though and that means I have to drill the hole.
That requires equipment, it makes a mess and it takes time. That’s why I charge $10-55 labor to install a replacement lock in labor alone. $10 is the cost if I can install the lock without modifying the door at all. This is a low price because you could do it yourself with only a hand screwdriver and 5 or 10 minutes.
You could also do the work if you buy a jig from the big box store and some hole saws. Measure twice and cut once though, the guy who installed the last one might not have centered the side bore on the cross bore. Don’t mess up your door by drilling in the wrong spot.