The connection from Victoria is a BUS, not a train! Round trip fare is £8 for easyJet passengers. Just say you're an easyJet passenger when you buy your bus ticket. No need to show your air ticket as you haven't got one!

£8 round trip is much cheaper than transit to Gatwick or Stansted or bus or train to Heathrow, and only marginally more than Underground to Heathrow.

The rail connection is from any station on the Thameslink line including Blackfriars, City Thameslink, Farringdon, Kings Cross Thameslink and London Bridge. Not bad for what the previous poster calls 'suburban'.