I don't think it is. Nowadays you can easily find sub $200 devices with "digital pots" that have perfect channel balance. The Motu M2, for example, is around $180 and does many things in addition to driving headphones.I guess that channel imbalance is slightly overrated.
People should expect more from such a simple audio device that costs $100+. I get that it's a niche market, so things tend to be more expensive, but still.