This is a question which I want answered, not a rhetorical question which I will try to back up one way or the other. I noticed that most all the weapons experience a big jump in power going from 3* to 4* (I know people say don't pay attention to the bar but when a weapon goes from [____] to [____________] that's a significant enough increase to safely say the weapon's a lot stronger). For 2* to 3* weapons actually tend to not change at all or not change very much o.O'''. You do get the benefit of having the cap on your weapon lifted later (meaning your damage will increase steadily as you go down instead of topping on at the terminal and decreasing till the town), but is this really worth it for 5* weaponry (with 3* stuff the 4* jump comes after so that makes it worth it)? From what I looked over semi-quickly it seems like 5* weapons don't get a very large power increase other their 4* precursors either. That makes the biggest theoretical benefit of going 5* be the fact that your weapon will continue getting stronger all the way to the core. Note though that most bombs get a better range when they go 5* so that makes it worth it however most swords and guns don't get a very sizable increase in power going 4* to 5* it looks like.
Is that really worth it I wonder? If you don't get your weapon forged by someone else (and omitting the forging cost of previous weapons) a 5 star equip will cost you 50,000 crowns (including transmutation costs), 300 units of your precious energy, and several tokens/hours/more thousands of crowns to get the ingredients if you don't already have them. All this just to get the cap on your weapon's damage pushed down to the core? I also recall reading many comments that talk about how T2 has better money and Heat than T3, and I *think* a lot of pros go for JK runs over core runs. So you use up all those resources to make a 5* weapon which will not be too much stronger than your 4* weapon and will get capped harder if you do T2 runs because it's a 5* weapon in a shallower depth than it should be used. That doesn't seem like a very good investment to me.
I've never used 5* weaponry myself so I'm asking here in hopes of finding people who have. Am I just being fooled by those ambiguous bars in the wiki, or are 5* weapons really not worth their cost?
Don't trust the bars. I think it's worth it, but I don't have any hard numbers to give you. Not like you want the crowns for much else after you have all 4* gear.
Also it's not only damage, but some weapons also gain some better effects/charge attacks. For example, going from atomizer to 5*status bomb is AWESOME.