Ticket terminology is used industry-wide among designers to denote basic scale & scope. It makes communication easier. What is what should be fairly common sense. It is all the things you note: cost, length, size, tech, etc.. There are no official specific guidelines or metrics, but scope is generally understood. Change in cost/popularity/tech over time also has an affect on unofficial ticket designation.
It is supposed to correlate with popularity but does not always. Therefore the disassociation from the Ticket-book days (which were based on demand/popularity) and the endless confused, fruitless and pointless banter on the internet about the ticket-level of an attraction. E.g. Ellen's Energy Adventure is now an unpopular E-ticket based on scale & scope, while Peter Pan is is very popular C-ticket in scope. If ticket books still existed these allocations might be reversed, based on demand.
Marketing is another group that often mis-uses E-ticket for hype purposes, e.g., calling Mermaid an E in d23 magazine.