MGibster
Legend
Sending Stones are an Uncommon item - so they cost a couple hundred gold and a couple of weeks to make. Or a hundred gold and a few days for an upper-level artificer. But, they are permanent. Watchtowers and people to staff them cost money too - using Lifestyle expenses as a guide, we are talking about one gold a day per watchperson.
I have to admit, and this is just a personal preference, that when magic becomes too common the setting starts to resemble the Flintstones with magic taking the place of dinosaurs or modern technology.