I did the math, and found that hiring a local lawn service was even cheaper, more reliable, and used less of my time, the thing I am actually optimising for. Efficiencies of scale still beat gadgets. Not to mention the care, and graceful handling of edge cases. This is to say nothing of the myrid other services they provide.
That said, I always dreamed of one, as a kid, who had to mow an acre. But as an adult, its clearly not the best option. Stop calling it an 'investment'.
Around where I live, you probably have to mow about 25 times per year. The lawn care people have quoted me about $70 per time to mow my ~1 acre yard. That's $1750 per year. It looks like, if these robots are able to become 20-30% cheaper then it seems like they'll probably be competitive with those people.
At some point lawn care firms will start to automate and the costs will come down. The idea that every landowner should own those devices that sit idle most of the time is a bit crazy if you think about it.
By the way, why do you /have/ to mow 25 times per year? Is that an actual requirement of some sort or really a personal preference? I live in central Europe (Berlin), haven't mowed a single time this year. Doesn't look particularly classy but it's not a jungle either...
The grass in my lawn (in Connecticut) really thrives in the soil here. If I let it go for a whole month in the may-oct range, then it becomes 12-15cm long and takes hours and hours for my little mower to get through.
Perhaps I just need to grow a different kind of grass?
I'm sorry that the idea makes you a little spicy, but words mean things and by any reasonable definition, and even if your particular situation does not validate the current cost of one (and bear in mind that this stuff tends to get cheaper), that doesn't mean it doesn't literally tick the boxes of an investment. Investments can even be bad ones, after all!
That said, I always dreamed of one, as a kid, who had to mow an acre. But as an adult, its clearly not the best option. Stop calling it an 'investment'.