Generally, the 1/e rule in this situation implies you should evaluate prices until Wednesday afternoon for the max sell price up to that point, and then sell the next time you see a price higher than that max (or Saturday afternoon whichever comes first). You won't always get the best price this way, but you'll perform better than any other know strategy. This strategy works with friends, too, as you can account for their prices in this strategy.

The only reason this may not be the best strategy here is that there are ways of having some information about future prices.

[1] https://en.wikipedia.org/wiki/Secretary_problem [2] https://en.wikipedia.org/wiki/Optimal_stopping