Can a commander be recast from the command zone an unlimited number of times paying the commander tax each time?

In the Commander format, whenever your commander would be put into the graveyard or exile from anywhere, you may instead place it in the command zone. This is a replacement effect defined by the Commander format rules, not the Comprehensive Rules proper, but it interacts directly with CR rule 903.9.

Each time you cast your commander from the command zone, you must pay an additional {2} for each time it has previously been cast from the command zone this game. This additional cost is commonly called the 'commander tax.' There is no cap on how many times you may do this — the cost simply keeps increasing by {2} each time (CR 903.8).

So if your commander costs {3}{G} and you have cast it from the command zone twice already, the third cast costs {3}{G} + {2} + {2} = {3}{G}{4} = 7 mana total. You can keep doing this as long as you can pay the ever-growing cost.

Concrete example: Your commander is Ghalta, Primal Hunger (normally {10}{G}{G} but with its cost-reduction ability). It dies and you put it in the command zone. You recast it (1st time from zone: no extra tax). It dies again. The second cast costs an additional {2}. It dies a third time. The third cast costs an additional {4} total tax. There is no rule preventing a 4th, 5th, or 10th cast — only your mana availability limits you.

The commander tax applies only to casts from the command zone. If your commander somehow re-enters your hand or graveyard and is cast from there, the tax does not apply to that cast, though previous command zone casts still count toward future tax calculations (CR 903.8).