How effective is putting something (like a pen) in the envelope?

[Sipe]

Seems like the idea of the dice became popular from the 7878 method. Apparently the business owners feel something solid in the envelope and it increases the chances of them opening the letter to see what it is. The idea makes sense but is it cost effective? Obviously I won't use dice because I personally find it unprofessional - especially since I own a business and the letters will be from the business. So I decided on a pen with the logo instead. Is it a good idea?