's business is definitely still boomin' in the off-season ... 'cause the NFL superstar just copped an insane amount of jewelry worth HALF A MILLION DOLLARS!!
You already know the Steelers receiver LOVES his diamonds ... but the dude keeps topping himself ... hittin' up his good friend Gabriel the Jeweler for the massive order:
-- Richard Mille watch ($190k value)
-- 2 more G.O.A.T. rings ($20k value each. Remember, he already had one)
-- 5-carat diamond earrings (50k value)
-- An insane diamond chain ($220k value).
Add all that up, and you have a haul worth a whoppin' $500k!