How do they get away with this amount of postage ?

https://www.ebay.co.uk/itm/MASQUERADERS-AIN-T-GONNA-STOP-RARE-NORTHERN-SOUL-45-M-/220871729327?pt=Music_on_Vinyl&hash=item336cfb20af

They don't, unless people pay it - I wouldnt

To be fair, the seller has quoted for priority service, which does actually cost this, though for a record of this value, he is hardly going to attract bidders abroad.