Learn Spanish (Latin America): El pedal es muy bueno para ser barato.

In this sentence, para is used to express a standard of comparison or a concession. When you say para ser barato (for being cheap), you are contrasting its high quality against the normal expectations for cheap things. We never use por for this kind of "considering that..." comparison.

Why do we use the infinitive ser instead of the gerund siendo like in the English translation "for being cheap"?

In Spanish, whenever a verb immediately follows a preposition like para, it must always be in the infinitive form. So, even though English uses the "-ing" form ("for being"), Spanish requires the infinitive ser instead of siendo.

Does the adjective barato have to agree with el pedal even though it's separated by para ser?

Yes! The word barato is still describing el pedal, so it must match its masculine and singular form. If we were talking about a guitar (la guitarra), it would change to match: La guitarra es muy buena para ser barata.

Could I use estar instead of ser here, like para estar barato?