We actually get a whole lot of benefits from being a member, rather than just the raw fiscal numbers you quote.
The CBI estimates that the net benefit of EU membership is worth 4-5% of GDP to the UK, or £62bn-£78bn per year. In 2014, the ONS reported that the EU, which is the world's biggest economy, accounted for 44.6 per cent of all UK exports of goods and services, and 53.2 per cent of the UK's imports of goods and services.