Stars migh be not that useful for pure melee, but it's kind of a narrow thing. if you say "if you do pure melee, you have no need of those stars anyway, so you might as well spend a bajillion on upgrading a lame weapon to be a bit less lame."
But on hybrid melee, or any other playthrough that is fine with boomerangs too (e.g. not pure ranger/mage/etc.) you wouldn't waste mana stars on that.
Plus, if you rise the fallen star cost of it, it would push that upgrade at least several days later in the game, by that time, you might got a good yo-yo, or a mace even if you're pure melee, and won't likely care about the boomerang anymore...
You can still get it on the first day, but if you don't have luck then on the second, while you can get a good weapon on the second day the boomerang still has it's range usage, but perhaps it would need a little damage boost for the crafting to work? Idk.