You list a guitar and for 10 days no one is interested until the last minute. And you pay more for an item by sniper bidding!! Most people let my guitars linger at ridiculous prices like £50 for 9 days... then bid £1000 in the last minute. But because the guitar was so cheap for so long, more people add it to their watch list and intent to buy it.
If you place a big bid early is deters other people because it shows your a serious bidder and also because the guitar is bid high early, people also still expect more bids near the end so they forget about bidding and look for cheaper ones.
When you sniper bid you can only surprise the seller with a higher bid than he expected. And take it from someone whose bought about 300 guitars on ebay, the cheapest way to get them is to bid early to deters others from intending to bid, email early and ask what they want, or use the Buy IT Nows provding they are no older than 12 hours.
