My last two phones (5 and SE) I just saved for and bought outright, upfront. All I pay for is AT&T’s lowest data plan (about $55/month for unlimited talk and text and 300MB(!) data).
But I am literally surrounded by WiFi everywhere I go (friends and family houses and even the two grocery stores I go to most). The only time I don’t have WiFi is when I’m driving…but guess what? I ain’t using/looking at my phone then anyway, so…
I’ve never used more than 120MB data a month.