Bicycle shorts are very much different than compression shorts. The two main things are they are designed to fit well in the cycling position and most importantly, they have a "chamois". Modern chamois is not made of genuine chamois, but engineered materials to provide padding and chafing protection. You should try to find at least a pair you can afford - look on the mail order sites and find something on sale for $25 - this will be better than any regular or compression shorts.