The only motivation I can see is: "well the competition charges a hefty recurring fee, so why shouldn't we", but then the competition isn't doing all that well for this reason. I see a lot of resemblance to Cisco's "Umi" product, which had a $25/mo fee as well, and was a total flop.
Most companies prefer to actually have a support plan, because if they don't, the alternative is to pay their own people to fix them, and it's usually cheaper to not pay someone full-time to have expertise in that area.
This is a business-focused product offering.
Note that this isn't very unusual either at most companies. Given the low failure rate of most electronics, it is simply cheaper for the business/IT team to buy a replacement Mac / router / whatever than to pay any kind of yearly maintenance fee, which is always designed to make more money for the vendor.
$250/year for a $999 piece of equipment is not a good deal. If it were an option, like AppleCare, most would advise you to not take it.
Despite that, I'd be very leery about purchasing this, as Google doesn't have a reputation for stellar support, or even _reachable_ support.