I would prob ditch it, I usually give a market a test between 100-200 hop to see if I can get at least one sale from it. Unless you try and presell it differently?
I think the OP question is a good one. If I can rephrase: "At what point do you stop pushing a product that doesn't convert?" Specifically taking into account the gravity. I have a similar question. I've driven several hundred hops to the E4E, which has high gravity and (per folks on DP) is supposedly converting well. And I have not gotten one sale. (I've used both natural and paid traffic.) Don't want to derail the topic and make this an E4E thread...there's plenty of those. But on the original thought, when do you give up paid traffic?
E4E has been converting well for me, again, see if you're targeting the right traffic, are you preselling the product? if yes, you may have a bad landing page, give more information
E4E does convert well. I had 2 sales in less than 100 hops. So either it's your landing page's problem or the quality of traffic.