Are you looking to carry or invest? You can get a simple (but not cheap!) Loveless or Lake knife or Michael Walker for around 5K. For "investment quality" knives, I would recommend staying with a maker that has already earned their reputation and whose pieces that have already started climbing in value. They may not double or triple in value in a year, but they can usually give you a reliable 5-10% escalation year over year. That's better than most commodities can provide.
For a really nice carrying knife, you can get some pretty impressive-look, perfect quality knives for $2k or less from many of the names mentioned above.
Or better yet, set aside $4K for a future purchase and use $1K to experiment with current production models. There are a ton of great choices in the market right now. You can buy and sell in the aftermarket and really get dialed in on what your personal preferences are. Then, after you've got a better feeling for the direction your collection tastes run, you'll have enough in reserve to really swing for the fences - so to speak.