As mentioned, you should never put your main phone on your bars. A cheap used phone, a few apps and you're in business. I switched 10 years ago, and will never go back. Locus all day long. Check the old site for tons of info on the app. It's hard to imagine something exists that does as much as locus does.
Costs don't even compare. It's dirt cheap to get going with a phone, and no you don't need a cell signal. It's true that Locus has gone to subscription. I'm going to say its worth it. The online web app is ok, but it's a great place for everything to live, like Garmins basecamp. Big difference is it syncs across all of your devices flawlessly. Regardless, there are lots of apps to choose from.
In 2015, I was riding in Newfoundland. My phone died. I found the closest big boxstore, purchased a cheap android phone, spent 30min at a Tim Hortons wifi and was back in business $105CDN later.
Charging is the elephant in the room with phones, imho. I switched to a phone with a massive battery over the summer. The first new phone I've ever used on the bike. It easily gets me a day of full brightness nav without plugging in. Wireless chargers are a good idea. Some are better than others.