For what it's worth: entered Chile (SCL) earlier this year on a US tourist passport. Upon entry, two separate stations added two separate items to my passport:

1. I had to pay the "reciprocal" fee of $132 that is charged to all US citizens (as punishment for the fee the USA imposes on Chileans coming the other way). The courteous and efficient folks at the reciprocal-fee desk (an easy-to-miss station before the actual customs/immigration lines) stapled a half-page receipt on page 24 of my 24-page passport. Page 24 is one of the four "amendments and endorsements" pages at the end of the passport, and in my case it was blank. I also had several blank visa pages, but the Chileans put the receipt on page 24 anyway. They also put a one-inch "paid" stamp directly on page 24.

2. At immigration, I got an ordinary quarter-page entry stamp, which the officer neatly placed on a page which was already half full. When I later exited the country, immigration put the quarter-page exit stamp in the last remaining blank quarter-page immediately below the entry stamp.

So, to summarize: "reciprocal fee" stamp and receipt used most of page 24, but it wasn't a regular visa page anyway. The entry and exit stamps used a quarter-page each, and were placed on a page that was already half-full.

Hope this helps.