No idea what shipping prices to Norway are for various options. Ignoring that variable...
I understand about the desire to buy the UM22-18. Its a sexy good looking driver.
Speaking practically, if you are looking to buy one or two subs because that's all you have room for, it makes sense to look at top notch drivers because the equation is simple... which gives the most performance at a price I can still stomach. The UM, drivers from SI, BMS, RE, many others are worth considering.
But when you start talking about a dozen or more drivers the equation starts to shift a little. There are now two valid ways of approaching it. One is displacement per dollar. Either you have a fixed budget and are looking to get the most displacement you can for that budget, or you have room for a certain max number of drivers and are trying to get the most value out of that purchase that you can. The other is surface area per dollar, because while the max SPL your system will be capable of is governed by displacement and available amp power, when talking about an array of drivers the real world everyday performance is going to much more closely follow surface area rather than displacement. Things like smoothness of FR across all seating locations, distortion, the mythical tactile impact that accompanies the sound are all more closely related to position and distribution of subs around the room and total surface area available. Cliff notes version... for a single driver in a box there are easily measurable and reasonably audible differences between a PA460, UM22-18, REXXX, and a Pyramid Pro Best Ever Woofer. But for a dozen drivers, other than the rare showoff session that is much much less than 1% of your listening time, there will be vanishingly small audible difference between the PA460 and Ultimax drivers. That's because running either at 1mm for a dozen or two drivers is going to be quite loud. A few mm is going to be as loud as you'd ever play them with the rest for headroom on the rare subsonic notes.
For the first approach, the UM22-18 is actually a pretty darned good value for the money. Better value per liter of displacement than the PA460 and most any other choices. An alternative to check out if you have the space to do an infinite baffle setup is the Ficar audio IB3-18.
For the second approach, the PA460 is a great choice. For any budget of Ultimax drivers, you can just buy twice as many of the PA460 drivers and have same real use output with lowered excursion, lower amp requirements, etc.
Neither approach is wrong. Ultimately everything becomes a budget choice. Your budget seems unlimited to many here, but even you would probably stop short of pulling the trigger on 16+ of the RE XXX drivers. All things considered, 16 Ultimax drivers are going to have more maximum output, plenty enough output at minimal excursion levels to not worry about that difference, and be a little easier to fit and distribution in a room compared to 32 of the PA460 drivers... but for a little more cost (maybe not that much more for you if you save on shipping half as many drivers).