I have to agree with you in this case. I believe it's good to consider the 80/20 rule.
The 80/20 rule basically says that...
80% of your followers give you 20% of your income, and...
20% of your followers give you 80% of your income.
That said, you want to focus 80% of your energy on the 20% that pledge on the higher tiers, because you're more certain that these guys absolutely love your work that they're sacrificing so much for it.
On the other hand, those of the lower tier are by no means less significant, but they aren't exactly very committed either. After all, I've heard stories wherein some supporters just make a pledge for a short time (until they get their reward), and then once they've gotten what they wanted, they stop supporting you. That's just insane! But it proves that there are those looking to take advantage.
So I think it'd really be better to leave the really good stuff at the higher tiers, and then limit them to a number of people (just to create a sense of scarcity), and give your general supporters something small and simple to look forward to and enjoy.