Then get the Centurion. Not sure what to say, I don't randomly or at all regularly spend six figures but when I have (like furnishing a new house recently) it's been approved. If I'm considering a really whoppingly huge purchase I would warn them ahead of time - but usually with a purchase that big you can get a discount for paying by wire/cash/etc. Hubby paid for my e-ring with a platinum Amex (Tiffany wasn't making any deals LOL).I have a platinum Amex, and this isn't true for all customers. I have a good credit score, but they won't approve my limit for an amount that high. I have relatives with the same issue, one in particular with a credit score of nearly 800 & a platinum card and Amex won't let him charge above 55k. Seems kinda like a catch-22...if you don't have a history of spending 100k, then they won't approve you to spend 100k.
Either way, sorry you had this experience although the Shay CS rep seemed to be quite distressed and sincere in wanting to help. Hope it all works out.