My father spent his retirement fishing. He didn’t need to fish to put food on the table, he just enjoyed fishing very, very much and it made his retirement more enjoyable. He spent a whole lot of money going out on fishing boats and it never once occurred to me that he was wasting money even though the expense was on an experience - something that had no resale value. It was not wasted money. It was spent on making himself happy.
If buying a better fretted fiver makes your playing experience more enjoyable you don’t need to justify it.