I've worked in the industry for one of the biggest online brands and can second this. It was not unusual to see a single customer spend over a million euros. We even had a couple who maxed the account limit of 5 million euros and had to create a second one.

These VIPs have their own account managers who often talk to them on a daily basis and they are given lot of gifts which are expensive (trips, luxuries etc) but nowhere near the sums they are spending.