Beyonce and Jay Z can't always get what they want --they've been unable to find the perfect L.A. home to buy ... so, instead they haggled their way into a rental for $150K a month ... and yes, that's a deal. They're familiar with the crib in ritzy Holmby Hills --it's the same one they rented last summer on a short term lease ... but our real estate sources tell us they just locked it down for a full year. We're told the power couple's been itching to move out of the Bev Hills area hotel where they've been living while house hunting --so they decided to go back to their old digs. 16,000 sq. ft., 7 bedrooms, 9 bathrooms and an infinity pool with a waterfall ... is one helluva plan B. You'll recall, Bey and Jay paid $200K/month for the pad last year --but we're told they dealt directly with the owner this time and knocked off $50K/ mo. ... based on signing a longer lease. Even the Carters love a discount.