The center diamond is one major variable
Origin, shape, carat, cut, color, clarity, certification, and current availability all influence diamond cost. A well-balanced stone can deliver a stronger finished look than maximizing one grade in isolation.
The setting has its own material and labor
Metal karat, platinum, band width, total gold weight, accent stones, basket construction, prongs, engraving, and finishing affect the setting quote. Complex custom work also requires more CAD and bench time.
A useful quote needs complete specifications
Share an ideal budget, maximum budget, proposal date, ring size, inspiration, center-stone preference, and wedding-band plan. That gives the jeweler enough context to recommend tradeoffs instead of producing a vague estimate.