A name sounds expensive for reasons you can almost point at: three syllables, a soft ending, a whiff of Italian or French. The names below carry that register, and people really use them — every one appears in public pet licence data.
The honest caveat
This is the one tag on the site closest to taste, and it is worth saying so. Whether a name sounds expensive is not a fact about the name in the way its syllable count or its licence count is. It is filed as a style because people search for it, not because a register recorded it — and if that distinction matters to you, the sound and origin filters are the measured ones.
Every count on this site is a tally of real registrations: pet licences and shelter intakes published as open data by New York, Seattle, Austin, Montgomery County, Cambridge, Zurich, Basel and three Australian councils. Popularity here is the average share a name holds across those registers, so a name common in a small city is not buried by one common in a large one. Nine of the eleven sources are North American, so read the ordering as naming in those places rather than worldwide.