Surely that depends where you bought it from? I don't know how it works in the US, but in the UK, certainly for large online distributors like Amazon, Play etc, they only take the money from your card when they ship the goods so there is no difference to you whether you pre-order or not.So it's not really $100 now or $100 later. $100 now costs you $5 vs paying the $100 later in the above example. Basically you are paying a penalty just to pre pay.
This may be different if you reserve an item in-store (I always buy online, a lot cheaper) but I thought a lot of shops only want a deposit up front, not the full amount.
Perhaps shops handle pre-orders differently in the US?
Steve.