Wrong and wrong.
Plasma is and always has been cheaper, simply because the technology is cheaper to manufacture. LED = LCD. LED only refers to the backlight present to increase the contrast ratio problem that never existed to begin with on plasmas. Each pixel of a plasma is individually illuminated, there is no backlight.
In fact, one of the biggest advantages to plasma is you can get a TV twice as big, with 10x the picture quality for the same price you would get an LED/LCD.
Also, most LEDs are marketing gimmicks that barely if at all help this problem. The really thin TVs that are "edge-lit" LED LCDs don't do anything. Only OLED, which to my knowledge is still very expensive to manufacture, fixes the contrast issue.
The manufacturers of LCDs are making great strides to eliminate the problems that plasmas never had to begin with
I will tell you that burn-in still exists and is one of the few flaws of plasmas, but permanent burn-in is a thing of the past. Still after playing a video game with a HUD, etc, for a few hours, if the screen goes totally black, you will see a slight ghost of it that will quickly go away.