Cost per mile is one lens. Space, speed, incline, and what keeps you moving matter just as much, and they point different people toward different answers.
Walking pads
Walking pads are the clear per-mile winners, at 3 to 23 cents a mile across our three models and three habits. They slide under a bed or sofa and suit walking at a desk. The trade-offs are real, though. The UREVO pads we priced top out at 4.0 mph and the WalkingPad Z1 at 3.7 mph, so they are built for walking, not jogging. The two cheapest models have no incline, while the SpaceWalk 3S adds up to 9%. User weight limits run from 242 to 350 pounds depending on the model, and UREVO's warranty is one year plus 180 days.
These are also the machines where a five-year horizon is most uncertain. We found no published lifespan data for walking pads. Even if a pad needed replacing once, though, the E1L would still cost about 13 cents a mile at 10 miles a week.
Tread Flex
The Flex is Peloton's answer to limited space. Tom's Guide measured it at 70.5 inches long unfolded and 37.8 inches folded, with a 0 to 12.5% incline. By our math, that's a footprint of about 16.4 square feet in use and about 8.8 square feet folded. It keeps the full 12.5 mph top speed and a 21.5-inch screen, but skips the camera, fan, and Sonos speakers of the Vision models. Peloton had not published its maximum user weight when we checked.
For a walker who wants real incline, room to jog, and the option to use classes, the Flex is the most affordable way into Peloton's ecosystem, with or without the membership.
Tread Vision
The Vision costs $1,300 more than the Flex and adds a larger 23.8-inch screen, a movement-tracking camera that powers Run Analysis, a fan, and Sonos-licensed speakers. It does not fold. Over five years with membership it comes to $2.50 a mile at 10 miles a week. Its extra features lean toward runners who want form feedback more than toward walkers.
Tread+ Vision
The Tread+ Vision is a different class of machine: a slat belt, incline up to 15%, and a Sled Mode that simulates pushing up to 300 pounds. At $9,694.40 over five years with membership, it is the most expensive per mile in every scenario, at $1.86 a mile even at 20 miles a week. For a dedicated runner or a whole household training hard, the features may justify it. For walking alone, the numbers make a harder case.
A gym membership
A low-cost gym sits in the middle of the pack at 44 cents a mile for Planet Fitness Classic at 10 miles a week, and it includes everything else a gym offers: strength equipment, other cardio machines, and a change of scene. What it can't remove is the trip there and back. If the commute is the reason walks don't happen, the per-mile figure understates the real cost.
For readers torn between indoor and outdoor walking in general, our comparison of walking on a treadmill versus walking outside covers the differences beyond cost.