Lexus invented the idea of a luxury hybrid utility vehicle in a version of its RX crossover well over a decade ago, but sales haven't been strong of late.

Cheap gasoline, better fuel efficiency from all types of vehicles due to rising CAFE rules, and a lack of interest in hybrids have all hurt the latest version of the RX Hybrid.

Now it has released prices for the 2019 Lexus RX 450hL crossover at the Chicago auto show.

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That's a new seven-seat version of the RX hybrid, with an extended wheelbase and a third-row seat that nominally lets the luxury crossover hold seven people.

Until now, Lexus had shown the seven-seat RX only with a conventional gasoline powertrain in its RX 350L form.

Now we know that the seven-seat hybrid mid-size crossover RX 450hL will start at $51,615, including a mandatory destination fee.

2018 Lexus RX L, 2017 Los Angeles Auto Show

2018 Lexus RX L, 2017 Los Angeles Auto Show

2018 Lexus RX L, 2017 Los Angeles Auto Show

2018 Lexus RX L, 2017 Los Angeles Auto Show

2018 Lexus RX L, 2017 Los Angeles Auto Show

2018 Lexus RX L, 2017 Los Angeles Auto Show

2018 Lexus RX L, 2017 Los Angeles Auto Show

2018 Lexus RX L, 2017 Los Angeles Auto Show

The hybrid version carries only a $3,000 premium over the starting price for the RX 350L, but that gasoline model has front-wheel drive, while the hybrid RX L gets all-wheel drive as standard.

Adding AWD to the gasoline model cuts the price difference to just $1,550.

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That's less of a premium than hybrid models carried in earlier years, when gasoline was pricier. Lexus has similarly reduced the differential for the hybrid version of its smaller NX crossover this year as well.

The RX 450hL has standard second-row individual "captain's chairs" for easier third-row access, but they can be replaced with a conventional three-position bench seat.

2018 Lexus RX 450hL

2018 Lexus RX 450hL

A Luxury Package, at $3,935, adds wood trim, LED ambient lighting, leather upholstery, sunshades on the rear doors, and special 20-inch alloy wheels.

The powertrain remains essentially as it was in earlier years of the current RX: a 3.5-liter V-6 paired to Toyota's two-motor hybrid system, producing a combined total output of 308 horsepower (versus 290 hp for the RX 350L).

READ THIS: 2017 Lexus RX 450h hybrid gas mileage review

An EV mode lets hybrid RX drivers run in all-electric mode, at low speeds and under light loads, for a mile or two depending on battery capacity.

Fuel-economy ratings for the longer L version of the RX 450h hybrid haven't yet been released.