People pay 50% more if physically present

They may be getting additional information about the product if it's in front of them, e.g. how comfy a shoe is.

This certainty in knowing that you won't have to return the item may well be worth a premium. Also, they're paying to get the item now, rather than in a few days.

I'm surprised the difference is 50% though.

They may also be less worried about defects in the product. Allowing someone to actually touch the product before purchase shows more confidence in the product than locking it in a glass cage.

Two words: Apple Store

This is said a bit in humor, and might be seen as a bit of a jump in context, but is the effect the article discusses a reason we have to have so many friggin' meetings?