Developers have long worked with starchitects on their luxury buildings, but some years ago they also began hiring top-flight designers to give the interiors the same panache as the exteriors.

Having the likes of Paris Forino, Ryan Korban or Lee Mindel associated with a building became yet another way to brand it as special — and worthy of prices that today can run more than $2,400 a square foot, compared to the norm of $1,500 a square foot, according to a recent Douglas Elliman report.

But while developers hire designers to add a signature style to differentiate their buildings from the competition, it doesn’t always work out that way: The apartments end up having quite a lot in common with others in the same market niche.

“Everybody’s looking at what everybody else is doing,” said Jonathan Miller, the president of Miller Samuel Real Estate Appraisers & Consultants, comparing the phenomenon to the so-called amenities war in which projects try to match one another in the number and lavishness of common spaces. Similarly, an apartment can be “really nice and special and unique — and not dissimilar to the other five places you just looked at,” Mr. Miller said.