You don't know the circumstances that generated this situation in the first place. It might have been a side-note that was lost during some point between development and testing and the final line into production.
Someone have obviously been sleeping to let it pass or not be updated on the game as a whole and think "Looks good... print!" or they may have left it out on purpose to save text-room and then either known for sure they had to errata it right away or it was caught in the up-drift.
I'm sure to veteran Commander players this is obvious, but I just don't get this card at all.
It'll always be a 3/3, won't it? Or are you going to have to run some wacky card that increases the casting cost of creatures so that you can get the most out of this guy?
When your Commander is exiled or sent to the graveyard, it returns to your Command Zone. Then, if you want to recast them, they cost 2 more for each time you previously brought your commander into play.
So he'll start as a 3/3, but if he dies and you replay him he'll cost 5 and be a 5/5, then a 7/7 and so on.
He won't have been cast so he'll etb with 0 counters and presuming no anthem effect (Heliod's Spear) he will be put into the GY as a state based action and may instead be put back into the command zone.
Starting Pool: (OVERALL TREND -1, -1, +3, netting +1 mana each three turn cycle to each color)
Mana Pool: RGG RGW (EDIT: the "RGG" part can be in any combinations of RRG, GGW, WWG, etc, just keep track of your colors for the combo!)
Summon Marath RGW
WAIT ONE TURN (unless past six mana sources/mana total)
Make 1 1/1 token
Make 1 1/1 token (Must be separate each time!)
Sac to altar (4 mana)
Exile Marath to Food Chain
Add to mana pool WWWW
Next steps are for the colored mana, since you wont net any colorless mana. (You will have enough Colorless mana to resummon Marath each time, as long as you go 1 token, 1 token, Sac both. Use only the colorless mana to do this. Do this pattern until Marath is 1/1. Then exile Marath to Food Chain).
You will always have enough to cast Marath with the Command Costs from the tokens it will produce and saccing them to the Ashnod's Altar. Just do this two tokens at a time until he is a 1/1 Marath,then exile him to Food Chain.
With this combo, you will indeed eventually achieve infinite mana. However, once you have the mana you require (if someone is butt enough to make you do the maths), Marath will still be on the board because you can't produce enough to remove all his counters (as far as I figure). If you want colorless mana boosting as well, mana echoes and adding a ivy lane denizen can be fun