Danneq
Headphoneus Supremus
That is the principle of diminishing returns.
Pretty much what vapman wrote.
And that the really good TOTL earbuds make you not feel the need for headphones since you come very close to the full size headphone sound. Earbuds can give you the best bang for the buck. But TOTL earbuds can also compete with full size headphones or IEMs.