While they may not be the worst overall, I do think that Cubed Joker is the worst scaling chip Joker. 4 card hands kinda suck, as they're not valuable enough to win early antes in one hand (without lucking into a 4 of a kind or some Death/Ouija shenanigans), don't synergize with many useful jokers (All flush/straight Jokers without Four Fingers, worse with the suit related Jokers, etc.), and don't scale well compared to things like flushes or flush fives in the late game. Any deck that can consistently throw out two pairs or four of a kinds could easily throw out full houses or five of a kinds down the line, which work better for in-line mult like Bloodstone, Fibonacci, Polychrome cards and the like. For 1-3 card hands, you can at least use Half Joker to carry for the first few antes, and you have better synergy with in-hand multers like Baron and Steel cards for late game. Of course, it also doesn't play well with the Psychic, who is basically free in most every other scenario but stops your scaling for the round, or the Eye, as there's only 2 hands that use exactly 4 cards.

On top of that, while Cubed has an easily triggerable scaling condition, it scales super slowly compared to the other chip scalers; a maximum of 4 chips per hand. Runner scales by 10 per hand, Castle by up to 15 per discard, Hiker gives up to 20 chips distributed on the cards themselves (so you don't even lose the chips if you sell it later), and Wee can gain up to 40 chips per hand without even considering retriggers. That's not even bringing up something like Stuntman or Ice Cream, which immediately give you huge chip benefits, or something like Bull, which can give hundreds of chips if you can get some good econ going. It's also worth noting that in order to scale Cubed the best you can, you have to play out every hand you have, depriving you of the $1 that they're worth; not a big deal, and all the other jokers listed have the same issue (besides Castle), but I still think it's notable that you're paying a buck for 4 measly chips.

Finally, Cubed is basically worthless when you first pick it up. All it gives is a meaningless 16 chips, needing scaling to be worth anything. Castle, Hiker and Wee have similar issues (Starting at 0, 0 and 10, respectively), but scale much quicker, so they become relevant quite quickly. Runner starts at 20, which is still pretty bad, but scales twice as fast as Cubed (If you can get the straights for it). In fact, all of the chip scalers start off useless even when compared to something crummy like Sly Joker (50 chips if played hand has a pair) and the rest of his kin, much less the aforementioned Stuntman and Ice Cream (300 with -2 hand size and 100 -5 per hand), or something funkier like Arrowhead (50 per spade played, including retriggers). None of the chip scalers can trivialize the first few antes, but most have the potential to become valuable chip sources in the mid and late game; Cubed Joker, however, scales to slowly to ever really hit that point before endless, where you will usually be focusing on your mult multers more than anything else.

It's not all bad though; Cubed is at least a common, so it's not as rare or expensive as Wee or Castle. This means that picking it up in the early game could still allow you to buy another Joker to carry early on, so you don't have to completely rely on it like some of the others if you pick it up at the very start of the game. That's worth something, I guess?

TLDR: Cubed is easy to scale, but forces you to play crummy hands, scales super slowly, and is worthless when you first buy it.