There are many ways for travelers and their money to be parted in the Monteverde Cloudforest area. It's not especially expensive to be there, it's just that there are many, many tourist activities available, all for a fee.
We skipped the butterfly gardens, the guided hikes in the national park, the Sepentarium and insect zoo, bungee jumping and a couple of zipline canopy tours. We did visit the Ranario (frog sanctuary) and the SkyTrek facility.
The Ranario was a great find, and for a small fee you get multiple entry to their many frog terrariums, so you can visit at different times of day. We went in the afternoon, and got a guided tour by a fluent English speaker who was very knowledgeable about the frogs as well as funny and entertaining. It was raining pretty hard when the tour was done, so we hung out for a while while our guide showed us videos of frogs and toads on YouTube until his laptop's battery died. We returned the following evening to look at the frogs in their night habitats, which was really cool. The frogs are almost all very small, so visiting a facility like this is a must if you actually want to see them up close and personal.
We spent the majority of our time and budget on a visit to SkyTrek, a zipline and suspension bridge facility in the cloudforest. I was worried that it would be overly developed, and the whole zipline canopy tour seemed just plain cheesy. As it turned out, most of the facility is a well groomed but wild trail though the forest, with several suspension bridges over valleys along the trail. We spent most of the morning walking this path, having many amazing birds, plants and insects pointed out for us by our guide. It was a fabulous hike, and was well worth the price of admission.
As for the zipline, it was surprisingly fun, though you really don't see a lot while whizzing over the treetops at 40 miles an hour. The views from the takeoff and landing platforms were pretty fantastic, though. The zipline package at SkyTrek comes with a ride up their gondola, which was very pleasant. I'm glad I did the zipline, though if I were going again I'd stick to the walk and maybe a ride up the gondola for the views.