So far so good. US Mobile has an unlimited talk and text plan for just $8/mo and silent.link is prepaid with bitcoin and is billed at rates like $0.002/mb. Since I don't use a lot of mobile data, my balance runs down very slowly. I only started last month, but I predict that my average monthly cost will end up being less than $15-20 per month total. Maybe even closer to $10/mo if I'm frugal.