You've asked a question that many would like to know , Dean .
I use certain data , even with high-end items , and I think it does matter !
In general , my experience leads me to suggest considering the following :
Lower-end items ...let's say $50.00 - $500.00 can be ones that folks who have to watch their money pretty close might buy .
Be mindful of considerations like household expenses (rent , morgage , and other monthly payments due) around the 1st & 15th of each month ; tax-time (& refund-time) , and paydays .
Higher end items , say $1000 - $10,000 are ones that I think about fiscal year stuff , quarterly taxes , dividend payment schedules , seasonal buying & etc . - sometimes these items can be attractive to 'the big boys & girls' , or the ones willing to use their credit lines to buy .
High-end items (to me , anyway) of over $10k ... timing matters to some pro buyers if international auctions are up-coming & the item would be a good 'hit' for them to sell at those auctions , for their business or customers .
I've only sold a few high-end items through eBay and found it much more hassle than private or pro auction service selling .
Ironlords input is valid , too .
Through the years , I've grown to think of selling antiques as more of an art , not a science .
I just keep it honest & do plenty of research .