Should every cost line in ARGUS Developer use an S-curve?

No. The S-curve is the right default for construction and the wrong default for almost everything else.

It spreads a cost slowly at first, quickly through the middle and slowly at the end, which is how a build actually draws money. A professional fee paid on appointment does not behave that way. Nor does a land payment, a levy or a marketing spend.

The common failure is not choosing the wrong curve on purpose. It is carrying the template default onto every line without looking. A curve is a cash timing assumption, so on an interest bearing project the wrong shape moves the finance cost, and the margin moves with it.

1. Go through the cost lines and ask, for each, when the money actually leaves.
2. Keep the S-curve where a thing is built over time.
3. Use a single point or an even spread where a fee or a payment lands on a date.