People buy because of the emotions they are feeling at the time. They will back up their decision with logic, but they buy because of emotions. This has been true since the beginning of mankind, and it will be true until the end. If you can get into your prospects head and know what they are thinking and feeling, all you have to do is supply a believable solution and they will buy. Most IMers try to sell. Ppl do not want to be sold, they want to buy. All they want is an answer to their problem, period. If you trick them, lie to them or mislead them, most will run, not walk, away from you. Learn to see life through your prospects eyes, think about life as they do, and adjust your efforts to suit them, and you will be well on your way to getting what you want.
You must get excited about your product for people to buy. Do your research, ask your customers do they want to buy, ask for their opinion, they will tell you the truth. Never assume anything always test before you invest.
Yup emotions, then logic. Plus they actually have to want what your offering. Demographics have a lot to do with it too.
In fact it is the moment of time when a person find what he needs, that is attracktive to him at this very moment... Sometimes we buy because we have to, sometimes we seek for a long time to buy one certain thing!
I'll have to agree with the emotions answer. People buy to remove pain points, to increase joy, to be accepted, for love, etc.. Of course from our standpoint, the sales page needs to be reminding them of why there NEED this product, and explain to them why this product is going to solve this problem. The reason they buy is emotion, the reason they buy from you, is how well you engage and satisfy the emotion.
You must ask what need or desire does the customer have and what value, result or reward do they expect.What do you do that is better than anyone else. Your competitive advantage must be something that your customerwants,needs,or values and is willing to pay for it.
Good copy and a good story. People love stories, and if you have a good one to tell then you can basically sell your story and people will buy it (your product that is).
Pressure will make them buy.... Tell them why they need it - then put a count down clock on teh page so they have only so much time to buy... I usually have a 90 count-down displayed for the user.