> Would a Default_Price = $0 have a special meaning? (mean that there is no default)

Yes, 0 means "no default price"

> Personally, I see the cost of the extra column to be exponentially cheaper than using an extra table .
> Further, I hate NULL in money type fields (I have a process with auto-creates triggers to ensure that
> money domain fields/columns assigns zero to the field).

I'm thinking in setting the value of default_price to null when price = default_price (in a before update trigger). I'm thinking this because I remember that null fields uses less space in the newer versions of FB.

So, do you think that's not a big deal, having the value duplicated in most of the records? I'm always thinking in having the database with no redundant information... but as a matter of fact I don't know if sometimes is "better" having some redundant values if this help me to simplify the "selects" later...

Sergio