Would not be surprised at $3k-$5k option price. Here in the US the gov is doing everything possible to discourage passenger car diesels. Do you have blue in oz ?
May be because the capacity is limited (gas stations that have diesel only have one pump for it against 8-12 for gasoline). That said it is much easier to find diesel than E85: one station in the metro Orlando area, now over 1 million residents + innumerable tourists currently $3.30/gal so 3/4 the mpg for 7/8 the price vs 87 PON.
Personally have stations with diesel within a couple of miles in three directions so finding is not an issue however the current price of regular is U$3.70, premium is U$3.90, and diesel is U$4.00/US gallon so takes an 8% hit over 87. Will need an EPA MPG rating of 18/25 just to be equal to the Pentastar.
Since the Merc ML-350 with a 3.0TD is rated at 20/27 & Jeep will probably be similar it will be lower in fuel costs than the Pentastar, $127/year difference (12k miles) or will take 11.6 years to payback a $1500 difference.
Doomsday scenario: Wonder how hard it would be to convert a flex-fuel engine to run on pure alcohol.
See also the EPA estimates