this is just my own opinion
i think for $10,000 to $40,000 salary players the market works like this.
seller's market begins at the 2nd or 3rd week of the season and ends at 2nd to the 4th week after the all star break. - give or take a week. - i think that is the best time to sell players.
it begins at the 2nd or 3rd week because i think more people are looking for 18 year rookies than veterans.
after that we go into a buyer's market. - where you can pick up players or staff at good prices.
it's at its peak after the trade dead line. which makes sense because alot of people know where they are going to finish in there league and want to dump players and staff to increase profits.
i think high salary players have a smaller market and it works different
that's my 2 cents - so take it for what's it is worth.