To be fair a 30$ knife is enough... Definitely don't buy those fancy japanese knifes for 200$ or so.

America's Test Kitchen did some extensive testing and found that the Victorinox Swiss Army Fibrox Pro 8" Chef’s Knife performed well above its cost. It costs around $50 (current $43 on Amazon), but they found it performed at or above the level of the fancier knives on the market. Their guess is that Victorinox had perfected a technique to make their microscopic grain of steel smaller, leading to a sharper knife and better longevity.

If you don't know, find the closest restaurant supply or head to amazon and just buy the Victorinox standard that is in basically every commercial kitchen everywhere. It's probably about $20-30 and will hold up nicely. Outside of that, I found a well reviewed amazon thing for around $35-40 probably about 5 years ago, and it's been great.

I'm going to add a little and say that almost every kitchen should have a honing steel and a basic set of sharpening stones. No knife is going to stay sharp forever.

If I had kitchen that didn't have these things, that is how I'd spend my $100.

It really depends because different knives are made of different grades of different materials, with different weights and so on. You want one that sits nicely in your hand, with a nice weight, that you can use without cutting the hand holding it. I'm a chef myself so I have a small collection of fairly expensive knives that are durable and stay sharper for longer, but I could be cutting food continuously for a good few hours in a day four or five days a week, so for home use you just want a midrange knife that suits you ergonomically and needs as much maintenance as you can be arsed dedicating to it. I'd say a honing steel and middle-fine whetstone might even be the better purchase, and to stop keeping your knives in a drawer and so on.