As for exchange rates... at $142 US, your driver is reasonably priced. At $1000US it is not, so do bear in mind that most of the membership of this forum is from the US, and those that who do business in dollars other than USD typically have exchange rates around 1.30:1 or so, so close enough for comparison. 7:1 is something you should probably make a note of when you post, as it's a bit out of the ordinary.
KP15LF is not the premium driver with which to compare, 3015LF is. With 9.6mm xmax, each one of those is worth 1.5 of anything around 6mm, even if it can handle 10,000w. Raw power handling and magnet size are basically irrelevant. They don't hurt as long as the other specs are in line, but it's not like a ported cab where bigger is generally better.
So.. to compare, you would have to compare whatever the price of the 3015LF is (let's say you come it at $350 per driver using the shipping methods we're talking about) to 1.5 of your driver... which would be $225, plus whatever the cost of 50% more materials for the cabinets is... and extra space to transport, etc.
That said, ShipItTo says that each 3015LF driver would be under $100 shipping when done in bulk, and there may be further combination discounts if you use their $50/yr plan. If you could get a commercial account with Parts Express, and arrange bulk shipping, you might find this to be more affordable than you think... maybe below $300 US per driver.
So with that in mind, using premium drivers might cost a bit more per driver, but there would be non-negligible savings in materials, time, space, etc.
As I said before, if it were that easy I would have done it already. Point is the sub that I have available could work in the cabinet. Now I could easily go to the store here and purchase it and head home to install. I have intentions of upgrading as I said in previous posts so I dont see it as an issue. I understand your point but I am not going to put my hat where I cant reach.