Sprint is offering to cut other carriers plan cost in half. But only for new customers.
I got a new S4 2 years ago. The Sprint stores were charging $200 for an upgrade. I was going to be in Europe for 3 months and I needed one of the world phones with a sim that Sprint phones normally don't have. Sam's had the same Sprint phone for $41 and renewing the 2 year contract. With data and the "My Way" plan (+$12 insurance) I was paying close to $100 a month.
Called Sprint to let them know I was bolting on the 27th of Dec. Plenty of used AT&T S4s for $150 and a $45 unlimited talk, text, and 1.5G of high-speed and unlimited low speed for free after the 1.5 was gone plan.
Sprint blinked first and offered a $40 unlimited text, talk and 1G of high speed and free unlimited low (2G) after that. No contract. It's unadvertised and the bastards won't put it on the table until you threaten to leave. I'm on wifi most of the time so I hardly use any data. Plus they're unlocking my phone