Learn Dutch: De verwachte winstmarge is eigenlijk niet onrealistisch. - The expected profit margin is actually not unrealistic.

This is a rhetorical device called litotes. By negating the negative prefix (on-) with niet, the speaker is actually making a strong affirmation. It implies that the profit margin is very achievable, and it is usually used to deliberately counter someone else's doubt or surprise.

How does the word eigenlijk affect the tone of this sentence?

Eigenlijk means "actually" or "in fact." In this context, it shows that the speaker is correcting a prior assumption. It implies that at first glance, the margin might have looked too high or impossible, but upon taking a closer look, it is surprisingly feasible.

Why does verwachte get an -e ending while onrealistisch does not?

Verwachte is an attributive adjective (placed right before the noun winstmarge), so it gets the standard -e ending. Onrealistisch is a predicative adjective (it comes after the verb is to describe the subject), and predicative adjectives never get an -e ending in Dutch.

Why is verwachte spelled with a single t, even though the past tense verb form is verwachtte?