In the base game of RftG, if you chose Consume>Trade as the action, do you have to trade on a card that has a $ ability? If it is a +3 and do you get +3 cards in addition to the normal trade value?
You first sell any one of your available goods for the number of cards indicated by the kind of good (i.e. 2 cards for a Novelty good, up to 5 for an Alien good). Some cards in your tableau may have Trade powers (marked with a $) that may affect what you get from this trade.
Then you must use as many of the Consume powers (marked with a IV) as you have on your cards as possible, on as many of the remaining goods that you have as you can. You can use these powers once only each, but you can use them in any order you like.
From the way you phrase your question, it sounds as though you think that the initial Trade is performed based on one of your Consume powers, somehow. It isn't; the initial Trade is a completely independent bonus and takes place before you refer to the special powers of the cards in your tableau.
Consume > Trade gives you access to a special phase that only players who select Consume > Trade can perform. During that phase, you must sell any one good from any planet in your tableau for 2/3/4/5 (blue/brown/green/yellow) cards. If you have any $ powers, those will change your payout for your single allowed trade, but you do not need any of them and the traded good can come from any world.