This may be true for some sellers but not me. I will always set my BIN at the upper middle range of recent sold prices with an acceptable best offer on the bottom end of that scale. My objective is to buy low and pass that savings to my buyers while still making a good profit on my end.
I (personally) know people that use the .01 auction start and I know other people that get top dollar for everything. The penny auction guy is a middleman, so of course the items he takes in to sell will command bids because they are upscale collectibles, as you mentioned. The my lady friend who sells at top dollar BIN only (no best offers), has been selling since ebay started and has a following of committed buyers. She is a very picky buyer and will only buy items in top condition. This is how she gets top dollar. Unfortunately she has end stage cancer and won't be with us much longer. Her sister is actually doing her listings now.
Agreed. There are ways to avoid all this crap if you actually take the time to do it instead of complaining about it. If you don't want to look at offers less than your willing to accept, then set your listing that way. If you don't want to sell to Luigi from Bologna, then set your preferences correctly.
Now, as for the original question...What do you guys think is a good rule of thumb for a best offer?
Myself, I usually set my BIN price 20-30% higher than the lowest amount I would accept.
Then I put that lower dollar amount in my best offer listing to "Automatically decline offers lower than$__"
This takes care of the stupid offers.