Possible Clues:

• Keep raising, at an auction
• Cause to rise, as a price on eBay
• Make pricier, in a way
• Raise the price of, perhaps
• Steepen, in a way
• Do a shill's job
• Make more expensive, as on eBay
• Make a lot costlier
• Make pricier at auctions
• Raise the price of, at auction