Yeah, I was the lead author on the study that originally looked at pythons' effects on mammals (look up "Holbrook and Chesnes Pythons on google). It's not good news, but there are worse invaders in the Everglades. Bounties cost money, and there are likely in the order of hundreds of thousands of pythons in SFL - The Water Management district is trying it out, but it's not going to be cost effective. The biggest problem to controlling them a little bit better is the federal government, at this point - Because all wildlife is protected in National Parks, so are the invasive Pythons. Only those with permits or letters of authorization can remove them from inside the national park, which is 1.3 million acres of prime Python habitat.
On the iguanas, they're not really a big problem in terms of the ecology (except in the Keys)- they thrive in disturbed habitats: canals, yards, etc. and drop off pretty quickly once you get to more pristine functioning ecosystems (e.g. the everglades). They're mostly just a problem for people's hibiscus (and, full disclosure, I'm sure they'd eat a fig if they could.) Key deer eat out of people's garbage on Big Pine - they wont be wiped out anytime soon ;-) They're like racoons in their range.
I don't mind the discussion derailing! - invasive species are fun to talk (and gripe!) about. Probably the biggest invasive problem in Florida are plants, Tegus and feral cats.