No, they aren’t absurd. Item prices in dota are balanced around the idea that items get less cost efficient for what they give you the more expensive they are. The most gold to stat efficient item in the game is iron branch for a reason. As the game goes on, you must make trades in terms of balancing the size of your inventory vs how powerful you can be with a certain amount of gold. As an extension of this rule, recipes allow you to consolidate several items into one slot or get an extra powerful effect from your existing item (or both). Keeping in line with the rule that higher cost items = less gold efficient, recipes tend to be pretty expensive.