Most bruisers have their mana costs adjusted. Only older tanks like Mao, Malph and Poppy still have higher mana costs on their core abilities. 55 Mana on Poppy for her Q is a lot compared to like 20-30 mana on many bruisers. And Poppy has one of the worst base mana values on top.
Most of the time items with like 900+ combine costs feel bad, especially when you have no single component costing more than 800g. If you want a high one time cost you have items like NLR or BF you add, you don’t need another 1100g for the combine costs. Just add one Tome (140 AP then in total like on the PBE) and you reduce the combine cost to 700g.
DC, Fimbul, Horizon Focus, …
Especially when such an item is your 1st or 2nd slot item. 4th or 5th slot is a lot different.
Too often are items niche because they have too high combine costs.