There's a reason why the 5C is not selling well, its priced too high. Selling it for more would be a bad move by apple. I'd have to say plastic feels like plastic regardless of what phone we're talking about.
I do like the look of the 5c, and there are different grades of plastic but its by no means a premium product. Moving all their phones to plastic would be a bad move imo
And plastic feels great. I'm holding my jugs right now during breakfast and they feel nice.