It's very possible. The charge multiplication rules can get crazy fast. With a lance and Spirited Charge, he's doing x3 damage. Rhino's Rush spell lets you do x2 on a charge, so that'd get you to x4.
Level 13 smite evil is +13. BUT, if you can get a survivable mount elsewhere, PHB2 lets you trade the mount for "charging smite" to deal 3x paladin level damage on a charge w/ smite instead of 1x. So now you have +39 damage. x4 will be 156 damage from smite ALONE.
Power Attack with a lance used in 2 hands is +2 damage per -1 to hit, up to your BAB in penalty. Now, this kills your to hit chance...unless you have the Shock Trooper feat, in which case it kills your AC instead (if the foe's dead, what's it matter?). Maximum possible PA of -13 for +26 damage x4 becomes 104 added damage from PA. Note, if you can find a way to make Leap Attack feat work while mounted (maybe if the mount also has it?) This figure doubles to become 208.
Base weapon damage... pretty simple, 1d8, x4 is 4d8, average of 18. If you have strongarm bracers to use a Large lance, base damage is 2d6, x4 is 8d6, average of 28 damage.
1 1/2 strength modifier is also multiplied by 4.
And he might have other static (non-dice) damage bonuses.
So, it's very possible. I don't know what he's using, though. Also, if he somehow has pounce, 350 charge damage REALLY becomes easy.