Quote - I'm planning on creating radioplays. My budget is $50 (for purchasing just the sound effects) and I want at least 500 various sound effects.

I looked at the amazon link and it did not have good reviews.

I think for $12 or thereabouts the 6000 sounds effects collection is pretty decent, the sounds are in various formats, and even if only 10% are in your expected quality and usability, you'll have 600 fer sure you like. It's an individual taste though. I though it was great when I was looking for cold wind (blizzard). Had several to choose from.

Check the review at gamedev.net too.

Or expect to pay more in the order of $100 to $250 for high end professional grade material