There's no need to spend hundreds of dollars on a sunrise alarm clock. Just buy some super-bright, flat white bulbs[1] and a timer[2]. (And a lamp if you need one, of course.) Sure, it doesn't get gradually light, but the main thing is that it's very bright when you get out of bed, which is really pleasant!
I don't think you have understood the point of a sunrise alarm clock. The reason they turn on gradually is to simulate sunrise, which makes it the most comfortable way for your body to wake up.
I don't know about you, but when I'm sleeping in a dark room and someone suddenly turns on a bright light, I hate it.
Different things work for different people, I guess. I think the clocks have two points, both aimed at simulating the conditions we evolved in--one, they turn on gradually, and two, they wake you up with light rather than noise. I personally don't care about the first point--my timed light flips on while I'm still asleep, I wake up gradually, and at the point when, in a dark room, I'd probably come up from a doze, roll over, and go back to sleep, I notice it looks like daylight in my room and get up. In fact, I prefer this, because the sunrise alarm clocks I've used haven't been bright enough to feel like dawn instead of a lamp.
Yeah, you don't get all the benefits of a sunrise alarm clocks, and it might not work for everyone. It's a hack to get some of the benefits at a lower cost, that's all.
I would LOVE to use the bedside lamp I already have to progressively turn on every morning at a specific time.
I'm sure there's a timer out there combined with a dimer that will replace expensive sunrise alarm clocks.
Concerning the nature sounds adapted to your sleepcycle, there's already many apps doing that for free.
If you have some crappy early-generation CFLs that have been used a lot, they can take 10-15 mins to come up to maximum intensity (although that max is still pretty puny, output wise).
I don't know about you, but when I'm sleeping in a dark room and someone suddenly turns on a bright light, I hate it.