Even for built systems the cost of ownership and maintenance will grow as the system grows. Take the logging example above and say you're using the Elastic Stack. Things are going pretty well and usage is increasing. Over time your system grows and logging is now present in all of your applications. You've seen your logging rate go from 100 logs/s, to 1,000 logs/s, to 10,000 logs/s and now are encroaching the 100,000 logs/s rate. Over time the amount it cost to host your ES cluster has surely gone up. You probably went from a single node cluster when developing the solution, to a multi-node cluster, to now a hot-warm-cold cluster with several more nodes than you originally had. You also have a dedicated team making sure your in-house logging solution is working and stable. The cost of ownership and maintenance of this system is real. Not only do you need to pay for the huge clusters you'll likely have a dedicated team supporting it. Most people I've talked to in the industry don't like maintaining their in-house logging solutions and would gladly pay for one if it wasn't for the fact that it was too expensive to switch then. Because you need specialized people that know this logging solution it's also hard to hire for this role when the person currently maintaining this system eventually leaves (because he doesn't want to do this anymore). At the end of the day it's cheaper to pay for a logging solution even if it's in the hundreds of thousands of dollars a year than it is to build your own.