*CTV was introduced in February of 2015*
CTV stands for Card Ticket Value, and is generally equal to the original purchase price, in tickets, of a particular card. For example, a card purchased from a ticket market for 25 tickets would have a CTV of 25, a card purchased for 10 tickets would have a CTV of 10, and so on.
In general, cards with a CTV will have a gold border around them.
It is also possible for a card to have a CTV even if this card wasn't purchased from a ticket market. For example, the Rats (computer generated 'players') can randomly add CTV to cards in their Packs, which you can then steal.
Cards won by playing FlipRat (a mini betting game found within PackRat) can have a CTV of up to 5 (or no CTV), even if the bet was made with credits. If the bet was made with tickets, the card can have a CTV of up to 750, or no CTV at all. Cards with CTVs won by playing FlipRat with credits are not permanently safe! But if you win a card in FlipRat by playing with tickets, that card will be permanently safe the same way that a card purchased with tickets from a market is permanently safe.
When you Feat (complete) a collection, you’re awarded with bonus tickets based on the total CTV of all the cards in the collection, and when the collection was completed. The higher the total CTV, the more tickets you get back! For more information on Feats and the tickets awarded for Feats, please read this article.
CTVs are additive, so if you have 3 of the same card vaulted, and all 3 have a CTV of 15, then those cards will contribute 45 CTV to the overall CTV of the collection. While you can always vault CTV cards even after a collection has already been Feated, this added CTV will not count toward the total CTV of the collection, since it's already been completed, and so you won't get any tickets back.