I was over-hasty in my comments --- looking a bit further just now, all the details I was looking for are in fact already available, here
In fact, 1:24k maps are included in that $550 price, which makes the cost a bit more bearable. You can send messages at 10 cents per message if you buy $50 worth (500 messages), which will likely be worth while for me next year, or 30 cents per message at 100 message for $30, or "a la carte" they're 50 cents per message. Spot "basic services" are $100 for a year, but they list a separate $50 per year for " track progress
". Since a basic checkin includes location, I don't see the point of "track progress", at least not for anything I would do ... ? My normal journaling site (postholer.com) already will accept Spot messages to update my location on google maps via that site.
The PN-60w unit itself weighs 6.7 oz with the recommending Li-Ion batteries. The Spot unit that accompanies it weighs 3.7 oz --- I assume without batteries, so add perhaps another 1.3 oz or so for those to get to about 5 oz (?), so on the order of 11.7 oz for the combination. Ouch.
Still, might be worth carrying for this particular trip.