Originally Posted by jason885

I'm in a similar situation with $5M/year of total spend but only $1M of it on Amex cards because I get such better value elsewhere.

If you're considering shifting $5M of cumulative spend but have an opportunity cost of 1% on it, you're essentially paying $50K just for the chance of the centurion business invitation even before considering the upfront and annual fees of the card ($10K 1st year + $5K/annual fee).

Since the platinum card already gives +35% rebate on airfare and you can have multiple cards, the incremental is only +15%. In simple math, spend $10K in Amex Travel airfare and save 150,000 points. I did a sensitivity table on this a while back and determined that if I amortized the $10K upfront over 3 years, subtracted some of the benefits to come up with a personal cost of ~$7k/year for the centurion all-in annual, then the incremental value of the 50% rebate vs the 35% rebate takes about $30k/year of airfare on Amex Travel to break even.

TL;DR: The math on opportunity costs are hard to make work if you know how to maximize spending elsewhere.