I'm totally new to road biking. I used to be hard core into spinning. I have the shoes with the Shimano cleats, heart rate monitor etc…. I trained in spinning about 4 days a week and really loved it. I got bored with it and decided to get into road biking. Which is why I am purchasing the bike now. My original budget going into this purchase was around $700. But that was before I knew what $700 would get me! I test drove 4 bikes last weekend. Two of the bikes were aluminum frames and two were all carbon frames (the Treks). See below for the bikes I tested. Of course, I liked the Trek Madones with the carbon frames the best. I could definitely feel the difference of the all Carbon frame and the way it rode. Am I crazy for spending about $1800 on a bike that I will only ride a few days per week? My goal is to get into group rides and ride maybe 1-2 times per week on my own after work. And then do some group rides on the weekends. I’m not sure if I am investing too much. I’m also afraid if I buy the cheaper aluminum frame bike then I won’t want to ride it because it’s too uncomfortable. Here are my stats: I am 39 years old, female, 5’8” and about 105 lbs. What bikes should I be looking at? Am I in the wrong ballpark?

1) Specialized Allez Sport $940 (not crazy about this bike)
2) Cannondale (not sure of the model) $1300 w/ aluminum frame and carbon fork.
3) Trek 3.1 Madone - On sale for $1,699 (all carbon - loved the feel)
4) Trek 4.5 Madone - On sale for $1,899 (all carbon - loved the feel)

I'm going back to try out the Specialized Roubaix, The FELT ZW6 and the Scott CR1 because they look like comparable bikes in the same price range.
Any help would be great! I am so new to this. All I know if some info I looked up online about what to look for in a road bike. Thank you!!