Generally speaking (in lots of areas of consumer products, not just this one) the higher up you go in terms of price, the less you're getting when you increase your budget by a given amount. And there are lots of good reasons to stick with budget gear! Especially if you want to experiment with different sound signatures, etc. If you haven't already, might be worth taking a look at "chi-fi" earbuds and IEMs by brands like Venture Electronics, KZ, Shozy, etc. Nice (but still affordable) earbuds are especially good competitors to the iSine because they can have excellent soundstage.
So true. So true. I have gone full circle over the years and am back to re-discovering budget gear in portable hifi. It's great. I can afford to try different designs in headphones, DAPs and dac/amps, where before each was a single major investment. I live in Canada but travel to US a couple times a year to visit family. Before I go, I always buy a couple items on-line and ship to the house to get the good US prices and save on shipping/duty. If I buy something that isn't my cup of tea, it's no major loss, and there's usually someone in the family more than happy to receive an audio gift. It's rekindled my interest in the hobby.