how much does captivate cost?

That depends on where in the world you live.  You should go onto the Adobe website and find the page that shows the purchase price for Captivate subscriptions and make sure the website knows which country you are from.

Be aware that due to the now very complex taxation legislation that is being introduced in some countries, you may find that there is no provision to sell a subscription license where you live.

I found the price options at Adobe Captivate 9-Buying Guide : monthly subscription $29.99 Captivate 9.

Full licensing, student/teacher price, upgrade from Captivate 8 are all at the above link.