Foam tips are probably your best bet for isolation and secure fit.

Yes, kilobuck iems sound a lot better than $200 iems, surprise surprise. Differences include quality of drivers, crossover, electrical components, acoustic engineering, R&D costs. Equally as important are build materials and Quality Control! For instance Symphonium Audio (and other true hifi brands) iems are made in metal, hand-assembled and individually measured and matched before shipping. That is another universe compared to the moondrops and truthears of the world, and is part of what you pay for with good reason.

The returns do grow smaller as you go higher, but you can always get better for more money, but more money does not always equal better. That is without taking preferences, subjective qualities and user hearing capabilities into consideration.

The biggest jump I’ve experienced so far was going from $200 iems to sub-kilo buck Andromedas.

Buy a pair of quality iems in metal housing, avoid chifi, take good care of them, problem solved. I wouldn’t call $150 iems expensive at all.

I usually buy stuff when I’m travelling to Asia.

How much did you spend in total on those iems, and if you could replace all of them for only one set (of comparable total value), would you do it and if so which model?

I see a lot of ppl here with large collections of chifi iems, and for me I always prefer just have 1 really good one until it breaks or I want to upgrade (shrugs).