For the life of me a I can't think why.
£69 basic plate + £67 for locks gets you to £136, plus hinges, plus making the enclosures etc, forming the stainless fog light guard all for £54. You could just buy the basic plate and get someone else to make all the rest up cheaper I guess.
I find £67 for two locks is just a bit extreme no matter what quality they are, I presume they're not gold plated. And as you pointed out earlier Chris there actually isn't an 'enclosure' it's just a hole (OK two holes) in the plate with a lid and lock.
I will have one for no more than £200 just to have a nice finish on the boot lid not because it's been hyped up!