For those of you who already have a favorite pair of nice earbuds, I suggest checking out ADV (https://www.adv-sound.com/pages/ciem). They are able to manufacture a custom-fit sleeve for a lot of existing earbuds and are therefore much cheaper (~250 USD). I have a pair of Shure earbuds and their custom-fit sleeves are great - they even send you a do-it-yourself ear impression kit, which is quite easy to use.