Xavier nails it. Estate sales have their own 'logic'. The folks running the estate sale put high prices on everything, and some of it sells the first day at the high price so they're not interested in fielding a lowball offer on day one. But after their sale ends, all of Grampa's junk goes to Goodwill or the pawnshop. One quarter of something is a whole lot better than all of nothin'.
I watch the papers for estate sales and try to hit 2 or 3 promising locations on a Sunday (usually the final day of the sales around here) I carry a tablet with several pages pre-printed with my name, hotmail email account and a daytime phone #. Most estate sales have tags on everything, just print out the tagnumber on the item(s) you're interested in, put in the description (serial number if you like) and write in your offered price. I write 'firm offer until (date about 2 or 3 days from now) on the sheet. I leave the offer sheet with the cashier, and say 'if you don't sell these items by the date I've listed, here's my firm cash offer'. The cashier isn't part of the 'grieving family', they're part of the estate sale team and won't be insulted by a low offer. After all, you're doing exactly what a lot of antique dealers do. You may not hear from them, but it's surprising how often I get a call doing it this way.
By the way, if you start attending a lot of estate sales, always check for old hand tools. I've picked up sets of chisels, files, shovels, axes, pliers, hammers, handsaws for next to nothing, and the metal is usually much better quality than the el-cheapo imported stuff at most home centers today.