- Both links refer to price not cost;
- There is distinction between natural gas and LNG; you can think of LNG as "delivery method" at the end.
- The natural gas prices are not provided with a reference to hub, etc. At least it is unclear. I would consult a renowned source such as Platt's or equivalent to analyze further the difference.
For sure the cost of liquefaction is included in the LNG price so is the transportation cost for pipeline natural gas (which is subject to economy of scale factor). Japan is notorious for being an important importer of LNG, they do not seem to have so many options there. Furthermore they have a lot of regasification terminals so the infrastructure is completely compatible with this mode of supply.