And that's exactly why guarantees are so effective for sellers. It takes that risk off the customers shoulder, and due to the "Oh, it'd be embarrassing to refund this app, since that means I made a mistake", very few people actually go through with the guarantee.
One pitch I found pretty neat goes roughly as follows.
Buy <product> now, and if within (30|90|365) days you at any point feel unsatisfied with it, feel free to ask for full refund, no questions asked, and you get to keep our <marginal cost 0 infoproduct>, valued X$, as a gift from us for trying it out.
Short breakdown of it.
"Buy <product> now" - bog standard call to action
"(30|90|365) days" - if the product is any good, longer guarantees usually reduce returns, since they give more time to grow on the product and forget the guarantee date.
"feel unsatisfied" - eg. you don't even need a reason to return it
"full refund" - that's pretty d'uh now, try a 110% refund for extra excitement
"no questions asked" - eg. we're not going to hassle you for trying to use this. you will not feel stupid.
"get to keep <infoproduct>" - even if you opt out, you get something
"valued X$" - with a home made infoproduct, that value is pulled straight from the posterior, but gives a value anchor
And suddenly that 3000$ product seems less risky than a 2$ app.