A.V.
Baby teeth are important. For one, without them to space out big teeth as they come in, the big teeth can come up in the wrong place or be crooked. Untreated cavities can become worse or infected. Sedation for small children is suggested when the work might be too much for a little kid. Friend's son was sedated for a lot of dental work when he was 5.
You might want to read the dentist's responses here: http://cyberdentist.blogspot.com/2006/09/they-are-just-ba...
Sometimes it is a brushing issue and sometimes it's enamel and sometimes it's both. My stepdaughter has a huge sweet tooth and is a lazy brusher and we shelled out nearly $3K last year for fillings and read her the riot act for not following instructions. My stepson hasn't had a cavity in his life. If you know the kid trends toward problems, you need to stay on top of them. My DD has my poor baby enamel but hasn't had a problem since the first (small, unsedated) filling when she was 10 months old. We've been seen a LOT but we've stayed on top of it.
And the long and short is if you think you're getting scammed, then get a second opinion but I would not just ignore them.