Forum:Yugioh Card Values Help?

Hello, I have several rare Yugioh cards that as far as I know from research, are authentic. I wanted to find out what they were worth though. Here are some cards I have:

The Winged Dragon of Ra (GBI-003) Magic Box of Death (P4-05) [In Japanese] Sea Dragon Warrior of Darkness (307-004) [In Japanese] Flaming Tree Man 18 (307-006) [In Japanese] Burning Weeds (307-007) [In Japanese] Leaping Grasshopper (307-023) [In Japanese] Illusionary Gora Turtle (307-011) [In Japanese]

I have searched all over the web to find accurate pricing but no luck. The Dragon of Ra especially varies, I have seen prices ranging from $20 to $3000. So I just want an approximate price on each. Help?