I had mentioned on a previous thread on this topic that I've found that once you're over the "good credit" threshold, I've found that a big indicator of what credit limit you'll get on a new card is what your credit limit is on OTHER cards on your credit report. Basically, the bank is "crowdsourcing" the decision of how much credit they can trust you with to all the other banks that have trusted you in the past (whether that's the right approach or not is up to debate). I think the other idea is you have to give someone at least the same, if not higher, credit limit as the other cards they already have or they won't bother using your card.

Therefore, its possible that DHH has some ultra-premium cards with 100K limits or whatever, while his wife does not, and despite having similar credit limits "the algorithm" says "hey this guy has huge credit limits and an Amex Black card, we better give him a huge limit too."