A place like Costco is undoubtedly way cheaper than that. $20 would be tops. And a lot of their movies are under that. You could do better at Barnes & Noble (bigger selection and good for ordering unusual titles--it's best when they have sales, but more expensive than Costco). Costco will always have all the new releases.
New movies are almost always about $20 except for in super high-end specialty shops (don't buy movies at high-end music stores--they charge like $30 for movies you can buy for half that). Old movies you can get for about $9, $12 or $15ish sometimes.
Or you can buy used movies at Blockbuster.