Spesh and Trek and the rest have big marketing departments, I wouldn't be so sure about their engineering departments. But they make a really good bike anyway, it's not rocket science. Despite what their marketing people say.

Someone charging only $1500 or even $2000 for a custom frame is living off of a spouse or has a day job or is living very frugally. There are very few people that are selling enough for a decent standard of living

As far as metal bikes go, you are probably getting a better bike from a custom builder. Although there are some very good Ti builders in China that are being marketed here. But the mass-market carbon bikes are really good, and if one of them fits you, that may be your best bet. If you want something special, a custom builder will make it for you.