I disagree. The UK was the third largest net contributor to the EU, and one of only ~10 member states that have historically made positive net contributions.
Its influence and role as a net importer from the EU will see it win a relatively favorable exit, including access to the single market.
The UK exit, in addition to the financial impact on the EU, will inspire many other member states on the verge of leaving to do the same.
The EU is already on thin ice, and the UK voting to leave may have just been the straw that broke the camel's back.