The real reason tiramisu can be so expensive

Tiramisu is a vital component to any Italian restaurant's dessert menu and can sometimes be rather pricy. Mascarpone cheese, a slightly sweet Italian-style "cream cheese" is one of the primary components of a tiramisu (via The Spruce Eats). Around half a pound is used for a single 8-inch cake (via Oh Sweet Day).

Although we don't typically think of Philadelphia Cream Cheese as a luxurious item, mascarpone, the real Italian stuff (cheaper domestic versions are available), can be quite costly at more than $7 per pound, and probably even more expensive at a specialty foods store (via Amazon). One way around this is by making it at home. All that's required is heavy cream and lemon juice, and a candy thermometer is strongly recommended (via An Italian in my Kitchen).

While many modern home cooks who make the famous dessert posit that the cost has to do with the cheese, the man behind the recipe has a different take.

The inventor begs to differ

Roberto Linguanotto, a Venetian pastry chef who is often credited with the invention of tiramisu back in the 1960s says that his creation is expensive because of the espresso used in another essential component to the dessert: espresso-soaked ladyfingers (via The Straits Times). If you aren't familiar, lady fingers are eggy sponge cakes shaped like, well, a big finger, the result of piping batter on a baking sheet to achieve the effect (via Joy of Baking). Linguanotto points out that each ladyfinger has to be dipped in espresso before being added to the cake and this is what contributes to the costliness. 

Consider that a shot of espresso is tiny, typically around 1 ounce (via Seattle Coffee Gear). Given the fact that ladyfingers are sponge cakes, it should come as no surprise that they act like one when introduced to a liquid, requiring a good deal of espresso be used. And don't forget that indulgent, and fittingly-expensive mascarpone cheese! All of these put together result in a pricy pastry, but a very delicious one likely worth the cost.