35 might be better than 25, but still much worse than dx240. This is speculation since it did not heard 35. Dx240 is indeed outdated, but it works pretty good. Don’t support system wide PEQ due to outdated Android.
I’m no longer using dx240 because bought Fiio M17.
Yes there are diminishing returns. But sometimes people feel that 5-10% performance worth 2x increase In price.
Also everyone point of satisfaction is different, because garbage 3 dollar earphone is much higher price to performance ratio than 20 dollar IEM gem like TE Zero.
Someone does not want to spend more than $20 because diminishing returns, some one spends no more than $300 because diminishing returns. Someone spends $4000 because fuck it.