What's the price (in USD) of the model whose L3 is 18 mb?
CREATE TABLE "table1_12740151_8" (
  "model_number" text,
  "clock_speed" text,
  "l2" text,
  "l3" text,
  "fsb_speed" text,
  "multiplier" text,
  "cores" real,
  "threads_per_core" real,
  "voltage" text,
  "tdp_w" text,
  "socket" text,
  "release_date" text,
  "price_usd" text
);
SELECT "price_usd" FROM "table1_12740151_8" WHERE "l3"='18 MB';