The cost to change a lock depends on a lot of variables. You will need a list of all the doors you are looking to change and what kind you are looking to change; the more secure a lock is, the more expensive it is. While Key on Spot Locksmith can deal with most needs, there will nonetheless be a discussion to determine how much the cost will be. Unless you are only changing one or two locks, expect to have a conversation about your needs, especially if you looking to integrate your door locks into a new security system.