Unless AMEX has lowered their membership standards, you still would need an income of $65k+ and assets of $10k+ to get an AMEX card...
Without getting too detailed about my personal life, I work a full-time engineering job, and run the coin business during evenings, weekends, vacation days and lunch breaks. The engineering salary allows me to have the card. The coin business puts the card to work.
It would only stand to reason that if indeed coins we're a good, or even somewhat feasible means of investment that at least one major firm would be offering this service or at the minimum using it as an index. But this isn't the case, anywhere or at any time. That tells me that even chicken entrails are a better investment than coins.