Whilst the way it was done was wrong, the guy selling is objectively charging too much. Aside from the pisstaking UK retailers, who are definitely not just dropshipping this, honest (DCA/Extreme) The gun + 6 extra mags can be had in the UK for about £740 brand new, or for those willing to import from Taiwan at worst case scenario, £580. These days, it looks like the latter is more likely to be the only option for those quantities, so this seller deems it suitable to jack up the price because of it.
USD to GBP based of at time of typing average conversion of 0.74 GBP to 1 USD.
Alu receiver WE SVD - https://kicbbgun.com.tw/en/pro_05_02.php?id=19870&category=184 - $292.38 USD = £216.14
WE SVD Magazine - https://kicbbgun.com.tw/en/pro_05_02.php?id=19868&category=307 - $ 48.12 USD = £35.57
Shipping for my last few orders of bigger parcels than this would ever be has been $60 USD with EMS = £44.36
So:
Cost for the gun and mags shipped in GBP: 216.14 + (35.57 x 6) + 44.36 = £473.92
Customs charge of 20% taken against whole value inc shipping at point of import: £473.92 x 1.2 = £568.70
Add the Parcelfarce handling fee of £12, resulting total: £580.70.
Or for UK, wait until Bespoke have the gun back in stock again, or will special order it for you:
https://www.bespokeairsoft.co.uk/we-svd-gas-blowback-rifle-plastic-faux-wood £379.99
Plus Z1 to have the mags in stock
https://www.zerooneairsoft.com/products/WE-GBB-Mag-for-SVD-20rds £60
£379.99 + (£59.99 x 6) = £739.93 (probably another £20 or so for shipping)