As an aside and not wishing to derail this discussion but machinery doesn’t always mean new machinery.
Many a golf course, especially courses with less funds available, survive based on secondhand maybe even thirdhand machinery.
It’ll be interesting to observe over time the life expectancy, replacement parts availability etc and the general re-use ability of robo-machinery. Plus more prosperous courses use trade-in funds as part of the process for obtaining new equipment.
Atb
Depending on the piece of equipment and its age/usage, I always feel that used equipment is a false economy. As a general rule I use around 2000-2500hrs as the point I don't want it anymore as at that point the maintenance ramps up exponentially or the expense stuff that is let go means that it is not running as effectively (as in production) or as safely as it should. I get that there is a market and need for them due to it being easier to swallow the lower purchase price and fix it as it goes rather than paying full whack.
As for the robots, right now there are two main types. The roomba type ones (thats the easiest description) that use razors to cut the turf and the recently launched Firefly which is the large reel mower thats more like what we traditionally use. I've demoed both and they are impressive. Anthonys links are great but there are a lot of variables in what they can and can't do. The biggest thing is as superintendents we have to rethink how we do things as the robots can make our traditional routines not as efficient. There are also many variables on the what works best where, but they are quickly getting there. For example -as Anthony mentioned - they can mow around 20 acres on a charge so generally not an entire course, however since they can run at night, and at odd times, it means that they can run more so in theory one machine can just keep lapping and mowing say 9 holes everyday than say 18 every other.
As Anthony mentioned the reel mower is about 60% more than its regular equivalent. I've demoed it and it is very impressive (on a side not the big boys are bringing out autonomous mowers soon too). When I did some quick math, in the mid Atlantic, labor is a wash over the 6-8 month season but there are some savings where they are run year round. The biggest savings are in fuel and servicing. There is very little to them and most of the parts are plug and play so they are easy to swap out. The (Samsung) battery is guaranteed to be at 80+% capacity after 7 years. The hydraulic motors etc on a regular machine start to wear sooner so I can see these machines lasting longer. The batteries are expensive but can be replaced so in theory you can replace the "engine" for say $30k after 8 years but since there are no other wear parts on them, in theory the rest of the machine will last longer too. The only long term maintenance item I might worry about is the brain running it but it looks like that can be swapped out easily enough too. Since it is computer based they are able to add more features without changing any hardware (and it's had a few big updates since I saw it in the spring). It's a very impressive machine and it'll be interesting to see how efficient they can become as people learn to use them most effectively.
The biggest labor saving is for those who are struggling to get labor as they can now do more things with limited staff.