The 333 only has a 66 Mhz buss and can be overclocked somewhat. Maybe that's why it's so expensive.
Oops, I just noticed that you are comparing a PII 333 to a PIII450. I thought you were comparing PII to PII. My mistake.
There really isn't any good reason for that. Slot 1 CPU's are all way too expensive. You can get a Duron for under $50!