Cost is often irrelevant to function. So if you've been led to believe that more $ = more cutting performance, that's generally not the case. A good production knife can potentially cut as well as a custom knife, occasionally better depending on a number of factors. Customs often feature better finishes, more options in blade/handle material and embellishments, and you can often design your own blade from the ground up. Generally you're paying for the fact that one very skilled craftsman built that knife from the ground up. Machines are used to augment the hands, not replace them.
As for American vs. true Japanese tantos, the difference is night and day. First, the word "tanto" describes a class of bladed weapon with certain defining characteristics. Blade shape varies within this class. There are curved tanto blades and straight ones, full height convex ground blades (more common) and blades that resemble short katana blades. In no form does the Japanese tanto resemble the Americanized angular shape, except in certain ancient (think 1000+ years ago) blades, and those are usually swords.
To address the price points you listed, $100 can get you something like an Emerson CQC-7, which is a classic American tanto folder. Not too much in good fixed tantos at that point, but something like the Spyderco fixed Lum tanto is available between $100-200. That's a more traditional shape, but its hollow grind and fittings put it closer to the American than the Japanese.
At $500, you could get a nice, simple folder from one of the more mainstream custom makers, or a fixed blade with a bit more embellishment. A large variety of stainless and non-stainless steels are available to you here. Damascus is a possibility, as well. Some production and semi-production pieces float around here, too.
At $2000, you can pick and choose your options, even with the higher-dollar smiths. Damascus, folded steels, whatever. Just put the money down and some smith somewhere will do whatever you want.
At $5000, you can have your knife plated with gold and studded with gems. You can also consider having your tanto made in Japan, by smiths who command that sort of price by government decree. Or you could have an American smith use one of his own teeth as a lanyard decoration. I know I'd give up a tooth for 5 grand. The point is, once you're at this level, you basically pry the field wide open. At least for something the size of a knife.
). Generally you will see better quality stuff come from custom makers, as they have pride in their work and won't something leaving their shop without being up to their standards (which is usually pretty high).
out of all the knives I have messed with I like the feeling of it the best..