I will say they are exaggerating(Lieing) before I say they got ripped off... 600 is extreme for a tank like that(I doubt they paid that)... I don't think I can even fit $300 dollars worth of fish,rock and sand in that tank.
they clearly are missing a few screws to begin with.
I say they paid 300 for it, and are trying to get their 300 back by making it sound like it is worth more.