There are some diminishing returns to consider. I think the difference between a $10 knife and a $50 knife is likely to be pretty obvious. If you can get up into the $80-$90 range, you'll probably see even more quality. But the difference between a $120 blade and a $500 model is likely to be less obviously dramatic.
To the collector, having a knife from a specific maker might justify the expense. To the workman, a high-priced safe queen might well be a waste of money.
When I'm at home and need to open a box or something like that, I'll grab one of the cheaper (albeit sharp) models. If I'm heading out the door and want a defensive tool, I'll grab one of the higher-end items. For me, "higher end" means something that retailed for around $80 or so MSRP - which I got for maybe half that.
Look, at the end of the day, we're talking about a sharp piece of metal. A solid knife from a good maker and designer made from good materials doesn't have to be in the high 3-figures to meet the needs of the general owner. If you shop aggressively and wait patiently for a bargain, you can get a very good knife for a reasonable price.