There are many choices available and yes, there are quite a few
good TTS voices in the under $100 category.
Some of the TTS companys do not list the prices of their voices
which tends to make me a bit aprehensive regarding their pricing.
A few of the voices I've tested have marked inflection, nasal tones,
trouble with double L's like "Jill" (sounds like a slight skip between
the first and second L. A couple actually sounded like the female was
in a drug induced state or at least extremely mellow and some were
sort of muffled and not clearly distinct in their pronunciation.
I do have some info regarding a few companys:
ScanSoft has acquired Rhetorical
Acapela has acquired Babel
The NeoSpeech voices are the same as the ones from Voiceware although
the ones I previewed from voiceware sounded clearer.
I do know that some companys will have background sounds , music or
noise playing to keep some people from using their voice demo for
commercial purposes. For instance...Type your text in their demo,
play it and record it for your own use, perhaps on a web site., etc.
Usually the purchased voice will be much clearer than the on screen
demo of that voice due to the above noise, bandwith considerations,
speaker quality, etc.
There are a number of Free voices available and sometimes one does get
what one pays for. The free L&H British Female voice is pretty good and
if one downloads the L&H voices one can get 10 variations of Mary, Mike
and Sam although theirs is not the best quality.
Cepstral offers 10 different US English voices for $29.95 (most are at age
30 except for one 9-10 year old child and one 12-13 year old child),
2 UK, 2 Canada, 2 German, 2 Americas Spanish voices.
AT&T offers Mike & Crystal with the purchase of their Speech Engine for
NeoSpeech offers Kate & Paul for $35.00 plus a lot of nice support products.