Assuming that all fonts have basic utility in common, there are several factors which determine the price at which fonts are sold. Some of these, like the amount of research and design time that went into the font, or the reputation of the designer, aren't really relevant to the average consumer. The characteristics which consumers may find meaningful are: Originality, Novelty, Specialization and Style. More expensive fonts will tend to rank very high in these four areas. These qualities characterize what we call 'designer' fonts.
Originality - Designer fonts tend to be original designs, less likely to be derived from other already existing fonts which you can find in one of those mega font packages. Original fonts are appealing to anyone who uses fonts, because they don't look similar to the fonts which everyone else is using. You want your publications to stand out from the crowd. Having different fonts makes them look unique.
Novelty - Designer font prices are strongly influenced by how new they are. The newer a font is, the less likely people are to have seen it before, which imparts some real value to that font. A new font won't yet have been cloned and made available from other sources. It won't yet have shown up in print or on TV. This means that if you use it first, your design benefits from having the look that font imparts before the competition. This is most meaningful to mass media companies, but it's a consideration even for small businesses and private designers. Older fonts are often discounted once they've moved out of the novelty phase of their product life.
Specialization - Designer fonts often have characteristics which you won't find in mass market fonts. This can include unusual additional characters, specialized weights, or multiple alternative versions of the characters. Perhaps most important, designer fonts are much more likely to have highly-tuned kerning and spacing which can make a world of difference in hos a font looks in print. Designer fonts may also be modified to meet unusual technical requirements for specific classes of users. These are things which not everyone needs, but which are of great value to those who do need them.
Style - Designer fonts are often stylistically more extreme or unusual than mass market fonts. They may be bizarre looking, or have a look which evokes a particular mood or subject matter. Extreme grunge, techno, hand-drawn calligraphy, script or decorative fonts are clearly set apart from the run of the mill by their unusual appearance. Day to day use may not demand this sort of font, but sometimes they're just the thing when you need a particular look.
These characteristics make a designer font more rare and unique than the average mass market font. If you just want utility text, Times or Helvetica will do the job. If you want a special look, you need a special font.
To some degree designer fonts are a more specialized product than bulk-marketed fonts, and they're made for a somewhat more sophisticated consumer. They are not going to be universally useful or have as large a target market, but those who need them will be willing to pay a little extra for the characteristics which these fonts have. Traditionally, the market for designer fonts has been restricted to advertising agencies, publishers and professional designers - big media companies. This is why some fonts cost hundreds of dollars.
The advent of digital technology has made it possible to broaden the availability of designer fonts and lower the price so that mid-range consumers who might find them useful can afford them. Today you see a proliferation of designer fonts in the $10-$30 range, much less expensive than most higher-end fonts, and within the budget of many hobbyists, small businesses and novice designers. New font foundries have sprung up which specialize in providing a high level of design originality at a mid-range price.
When you buy a CD with hundreds or thousands of fonts for only a few dollars, what you are getting (assuming it's not a pirate font CD, which it might be) is second-quality versions of the most common, debased fonts in the marketplace. To beef up the font count on the CD you'll also be getting multiple variations of the same fonts, and similar fonts under different names. What's more, many of the fonts on the CD will be duplicates of the ones which came with your computer or with software you already have. You're paying a low price, but you're getting ugly, worn-out fonts you probably already have. You get what you pay for.
There's a place for thse CDs in the market. They're a way to establish a basic library of common fonts for pedestrian uses. But don't expect to find anything exciting or special on these CDs.
When you pay a few dollars more for a designer font, you're paying to get a font which is special. It's not a font which everyone already has, or which you've seen around for years, or which looks just like every other font. It's going to be a font which fits your unique needs and has real style. That's worth paying for from time to time.