Okay here's what I've found out so far...I'm not a resident of NC (yet!) but we are looking to move there so I've done alot of pricing on houses and looking at schools, etc.
First off, I don't think you could really call RTP "coastal" at all - it's about 2 hours from the coast - so in case what you really want is better access to the ocean, then you'll have to look further east.
NC is going up in price because of the "half-backers" - retirees from the north, who bought in florida but find the summers there too brutal - so they buy a house in NC to get the "cooler" weather of some parts of NC (mostly the mountains). So many of the mountain town (in the west) have prices that are higher than the actual economic opportunity that is there (like Asheville).
The Triad is still fairly affordable along the lines of what you mentioned (155k and up)...the schools are a bit spotty there and some of the cities have some crime issues, especially for their size. So you just have to find the right neighborhood. But it's further from the coast.
Charlotte is a typical big city with some crime, some lovely areas, and price points all over the place. So again, it would depend on the neighborhood.
RTP has a fabulous economy but the houses there are not as cheap as they once were. If you are looking in the 100k-200k range you will have a limited selection. We are in the 200k-300k area and I'm having a hard time finding non-HOA 3 bedrooms close to a city center....but if you like the "new built" suburbs, there are lots of options in the price range. The schools are pretty good all over the place - except for a few areas of Durham or Raleigh. The Carrboro-Chapel Hill schools are "excellent" but are VERY academically intense.
Other areas you could consider (which I haven't done too much research on but did look at initially) are Wilmington (which is ON the coast) or Greeneville (closer to the coast and has a supposedly thriving art community).
We've also looked into a few small towns between RTP and the Triad - hillsborough, burlington and Mebane. Schools are spotty (depends on neighborhood), COL is lower, and they are all within striking distance of bigger areas....I'm very interested in Hillsborough right now...but I haven't been there yet.
ETA: Also there's a cool little town called Wake Forest in the RTP area that is more affordable and has a historic little downtown and a farmer's market - it's really cool-looking but not as easy to commute to all the "jobs" on the west-side of the area thus it's lower COL
I strongly recommend the website www.city-data.com
- their forums on there have ALL kinds of info about towns all over the country...the posters tend to be a conservative lot so take their opinions with a grain of salt if you are a more liberal persuasion (that's why I prefer the OPINIONS of the MDCers! but city data is good for facts)- but I've found great info on jobs, housing, and schools on there.
ETA: we are moving from california so we see NC as very affordable - but if you're coming from a lower COL area it's getting harder and harder to find those same "cheap" places that were there 10 years ago - have you thought about TN? I'm from there and it's still CHEAP there - especially east TN. Of course it's not on the coast LOL