You can find flights in August for cheap, just have to dig through their very bizarre website to be able to search those dates. I think I got there by finding flights from a particular city for an advertised month, then modifying the date ranges within their search results.
I found NYC to Reykjavik for about $280 on dates around worlds (allowing for a week stay and leaving the day after worlds). Would probably be worth getting to a city Wow Air flies out of and then taking their cheap flight if you're on a budget.
I'm actually going to be in Iceland quite a while.. my wife is coming with me and she has to be back for work by the 31st of July so we're going to do a week-ish there then she'll leave and I'm sticking around until after worlds.. pretty excited to have 9+ days to drive around the country and do some photography without anybody bugging me about being too slow