Many countries (Chile, Brazil as examples) with $100 visa fees for US citizens / residents have instituted
reciprocity fees -
they charge what the US charges their residents to visit the USA.
There are ways of maximizing these - Chile makes it easy, as your passport will be valid for Chilean visits for the remaining life of your passport (up to ten years.) For others, you can often purchase a multiple entry visa - it took me a short trip to the Indian consulate in San Francisco, and picking up the passport in the afternoon, to get a ten year multiple entry visa I can transfer to a new passport.
For Brazil, I found it quite easy to get a multiple entry visa good for five years - $100 for a single entry would be a bit much, but it's easy to get a multiple entry visa if you know about it.
Two sources I use for visa information include:
Delta Airlines Visa & Passport Information pages (select your country of citizenship, and your destination, for very good information
and
Travel Document Services (a commercial visa service I have found very reliable and cheaper than, say, Zierer, where you can see the requirements for US residents and download most visa applications.)
Would I worry too much about paying a visa fee, and even fulfilling requirements I feel onerous and ridiculous (are you reading this, Mr. Putin? Russian requirements are
very reminiscent of a police state
for a destination I had business in or wanted to visit, particularly given I may be spending thousands of dollars on flights and accommodations? I don't think so!