Papuan (or Irian Jaya) carpet pythons stay small and share a lot of the features i've seen you mention (inquisitiveness, can be purchased for under $200 etc). They are semi-arboreal and will climb a lot, especially when young. They also have a lot of variation in their pattern/coloring as well, which is fun.
I actually own an IJ LOL! She’s my little girl. You are certainly right, carpets are very inquisitive. Maybe a snake with a more lazy reputation to complement my carpet, like a Dum or SSTP