Here are some numbers and analyses regarding the economics of the Kennedy Space Center Visitors Center.
According to "KSC Visitor Center counts down to launch of new attractions", Florida Today Space Online, 28 Jun 1996, the KSC Visitors Center invested $80 million in upgrades and has a goal of 4 million visitors per year (up from 2.2 million before the upgrades). According to that article sales were $26 million in 1995, so if we back-of-the-envelope that at $13 per visitor, then adding 1.8 million visitors would bring in about $23 million more in revenues per year. It is hard to say much more about that without knowing more about their expenses, but as a first guess the numbers seem to work (which is what you'd expect since this is private money which is funding these upgrades). Note that some sources will mention a figure for the expansion more in the neighborhood of $35 million; according to the above-cited article that is for the building alone, not including other facilities like the new restaurants. Based on "KSC Visitor Center sees surge in interest", Florida Today Space Online, 16 Feb 1997, it would appear that they will be well short of the 4 million visitors in 1997 (but it is hard to say without more information on how visitorship varies seasonally and how long it generally takes for a new attraction to take off).
"Two new Kennedy Space Center attractions allow unprecedented public access to real working facility", Kennedy Space Center Visitor Complex news release, reprinted in Florida Today Space Online, 15 Jan 1998. The main thing I saw which might have been relevant is an explicit statement that this was not funded with taxpayer dollars. Other than that, more or less covers the same ground as the rest.
"New KSC tour attractions bring visitors closer to space operations", KSC release No. 9-98, reprinted in Florida Today Space Online, 13 Jan 1998. This time they aren't so rash as to forecast specific numbers of visitors. Depending on how things break down seasonally, 200,000 visitors/month might be something like 2.4 million/year.
"Two New Tour Sites Now Under Construction at KSC", KSC release no. 64 - 97, reprinted in Florida Today Space Online, 15 Apr 1997. Seems to indicate commercial interest.
"KSC shares `breathtaking' view; observation tower to present panorama", Florida Today Space Online, 27 May 1997. Might be nice to have the $14 million figure around...
"KSC Visitor Complex rockets into 30th year", Florida Today Space Online, 31 Jul 1997. This has some visitorship numbers--10000/day and 2.4million/year (they seem to contradict each other, but if the business is seasonal not necessarily. Alternately, it might be evidence of growth in visitorship).
"Astronaut Hall of Fame poised for major expansion", Florida Today Space Online, 29 Jul 1997. Contains the # of visitors/year for the Astronaut Hall of Fame.