贵 stands on 贝, the cowrie shell that was ancient China's money. What cost many shells was 贵 — and what cost shells to honor was also 贵: expense and esteem sharing one character.
您贵姓? 'your honored surname?' is the polite way to ask a name — expensive words for respected people. 贵人 is a benefactor who changes your luck. Haggling begins with 太贵了! 'too expensive!' — the four most-used syllables in any Chinese market.
A pile of money-shells 贝 — EXPENSIVE, and therefore HONORED.
贵姓 'expensive surname' for 'your name, please' shows Chinese courtesy logic: everything of yours is elevated, everything of mine is humble — my surname is answered with a plain 我姓...