I rolled four natural 20's in one evening three of those being combat critical hits. I've not been keeping detailed records and conducting statistical analysis, but this d20 definitely seems to be rolling high compared to its predecessor. There are two explanations. First, my intimidation tactics worked, or second, the dice isn't as balanced as it should be.
I read somewhere that gaming dice are not made to the same high specification as Gambling dice and that small imperfections such as air bubbles or irregular edges could 'unbalance' the dice. Another possibly more plausible explanation is that my dice have swirls of colour within them. Two or more coloured plastics have been blended to create this effect and of course the density of each component may be different. The variation in balance for such dice is likely to be tiny (less than 1%) but could statistically bias towards a particular number and would not necessarily be positive.
My new d20 clearly seems to be balanced towards better rolls, but is it cheating? Well if I'd gone out and bought loaded dice then yes it would be cheating. But this was just the luck of the roll (no pun intended) when I bought this set of dice and not the set next to them on the shelf. Most regular gaming dice are probably unbalanced but not to statistically significant levels. So every gamer has an equally random chance of buying a slightly unbalanced die that rolls high. The trick is identifying the bad dice and eliminating them from the gene pool so that you will be left with the high performers.
The moral of this story is that it doesn't matter how much you paid for your dice. In the end it all comes down to luck.