I notice on the
Avocet▸ Line User Group website that there is a half price offer until the end of the year for travel from Exeter to Barnstaple (it's not on the
Tarka▸ Rail site unfortunately, which would appear another obvious place to publicise it). They're also publicising the Over 60s offer mentioned elsewhere on the forum.
http://www.avocetline.org.uk/category/news/However, on the online journey planner and
GWR▸ ticket site tickets are still being sold at the full price of £10, which appears rather unfortunate.