Based on the TF2 Spreadsheet, and my experience in trade servers and trade websites, it would seem that most craftable items sell at much lower than the cost of crafting them or uncrating them. For example:
- A random hat costs 2.66 refined (2 craft hats) to craft, but the average craftable hat sells at 1.33 refined.
- A key sells for 2.55 refined. The average item you get from a crate, by my calculations, is worth around 1 refined. Unusual items are worth much more, but the probability of getting one is only 1%.
Is it ever statistically more profitable to craft or uncrate, rather than just buy the items you want via trading?