This really is a miniaturized version of the Model S. Just like your standard Tesla, the kids version comes with different battery sizes. If you want "50% more playtime," then you can pony up 50 bucks for the premium battery pack. The standard li-ion pack from Flightspeed is 140 Wh, but premium pack is 190 Wh. So, let's call it the P190D. There are also working headlights, a music player, and it comes in three "authentic" colors: Midnight Silver Metallic, Deep Blue Metallic, and Red Multi-Coat. The main difference? The Radio Flyer has two different top speeds, depending on parental settings: 3 or 6 miles per hour.
The Model S Radio Flyer starts at $499, but if you spec it all the way to the top (with one extra premium battery), it'll cost $804. Designed for ages 3-8, the battery-powered Radio Flyer can hold up to 81 pounds and it starts shipping in May.
If you'd rather buy a Model S toy that looks pretty on a shelf instead of the sidewalk, there's always the die cast route. If you want an electric kart with a bit more speed, that Actev Arrow goes up to 12 mph.