0 credit exchanges are often held alongside other gift exchanges which cost credits. With a 0 credit exchange, you can earn a credit through completion but it doesn't cost any credits to sign up for the exchange.
The recommended spend of 20 dollars does not apply to 0 credit exchanges.
Some examples of 0 credit exchanges we have had in the past are Stickers, Holiday Cards, and Postcards.
If you are one of the awesome Santas who decide to be a rematcher for a zero credit exchange, please note that for these exchanges, we often have more rematchers than we need, so please be aware that you might not be matched. However, we always need more rematchers for credited exchanges if you don't get matched and still want to give!