On the same page the 55" LG Smart 3D OLED was on sale for $2,299.99 ($3999.99 less $1,700).
The American TV companies lost money and let the Japenese take over. The Japenese lost money and are letting the Koreans take over. The Koreans will likely yield to the Chinese. The TV business has been bad for a long time.
The problem is you are comparing Samsung's budget Qdot tv, the 7500 model, to the OLED model. The fair comparison is the 9500 model, which is on sale this week for $5000 (regularly $6500)
There is an interesting article about the annual best television review held at CE week in NYC last week. Four companies (LG, Sony, Samsung and Panasonic) had their best tv's calibrated and rated by both video pros and the public. Pros and cons for each were reviewed along with an overall rating. http://www.bigpicturebigsound.com/LG-s-OLED-9600-UHD-King-of-TV.shtml