I'm inclined to agree that if you have 200 fracs and 200 $1s getting 300 $5s is a lot, averaging 70 chips per player, but in practice, one or two players will amass a pile 2x the average in physical chips.
However, if you are planning on using the set 20 years from now, you may not be using the fracs anymore. $100 in 2004 is about the same as $162 today, and that (aside from the recent correction), is well below the historical average. If you are playing a 25¢-50¢ game today, in 20 years, you could expect to be playing 50¢-$1, and that is if your disposable income remains constant.
If you are in college or a recent graduate, you can expect to have considerably more expendable income in 20 years, and may want to increase stakes accordingly. If you still have children at home, in 20 years, you will likely find that you have a lot of extra income because you are no longer feeding/clothing/paying for education of those extra people. In that case, $1-$2 games may be your preferred stakes. In that case, those fracs will only play for family games, or for high variance games, and you will want the extra $5s in play as they will be the workhorse chip in the future.
Of course, you could always get another set in 20 years, but will Paulson, or CPC still be making clay chips then, or are you going to look back and bemoan "why didn't I buy MOAR chips?"