Amex probably has a database where they rank stores/services/properties.
The more it falls into the disposable income file, for example, staying at the Ritz instead of Motel 6 in the same city then the more likely they see it as luxury spending vs 'they-had-to-stay-somewhere' spending.
Personally I probably spend the same I would have in year but now do it only a few times. Another example, instead of buying several bags, trying to figure out which one works best, and spending $300 over the course of that time, I only spend $300 once on the RIGHT bag at Tumi. Thereby saving myself grief from the back and forth lol.
With enough research I find that the right luxury item ends up costing me less in the long run. Yet it still counts as a luxury item in Amex's eyes