I acquired Referable and other big domains by reaching out to the owner directly when they were not listing it. That's the best way to get a discount. Regarding Flippa, if you bid and it doesn't get accepted, try following up with them in 2 months via LinkedIn, email, or phone (search Google for WHOIS DomainName to find contact info). They may realize by that point that they are not going to get as much money as they were hoping for and be willing to part with it for less - especially if you establish a personal relationship and rapport, and they believe in your vision for the URL. Funny, but it matters to many people (domain squatters not included).