To understand why they did the unboxing, and why it was a really smart thing to do, you need to look at the payments they get from YouTube.
They previously unboxed a 40 year old Honda, that YouTube video has made them $58,100 so far. They unboxed the most expensive street legal bike on Amazon, that video made them $53,900. Incidentally, that bike cost them $2,495. They unboxed a $3,500 dirt bike, and that video has made them $105,000.
After just 2 days up on YouTube, the Norton unboxing has made them almost $3,000, so they are making around $1,500 per day, and money will flow in for as long as people keep watching at this level. So whatever they lost in the value of the bike will be recovered in the first week up on YouTube. By the end of the month, YouTube will have bought them the bike and paid them for their time. Its a good business to be in right now.