Lana Del Rey Sang at Kim Kardashian's Wedding ... For FREE

Lana Del Rey shot down the ridiculous rumor she scored an insane pay day for singing at Kim Kardashian's wedding to Kanye West ... telling TMZ she did it for nothing.

One report had Lana's fee at a whopping $2.8 million ... but this afternoon at LAX, a very friendly Del Rey told our photog she didn't receive a dime.

Lana also explains WHY she performed gratis, and the good news is -- there's a slim chance she could do the same for you.