Is there any consumption cost when you add a stream to a table in Snowflake?

Snowflake extends the data retention period for the source table temporarily when a stream is not consumed regularly.

Regardless of which edition of Snowflake you have on your account, if the data retention period for the table is less than 14 days, behind the scenes it is extended to the smaller of the stream transactional offset or 14 days (if the data retention period for the table is less than 14 days). But your monthly storage charges will be impacted if you extend the data retention period.

A stream's main cost is the processing time used by a virtual warehouse to query the stream. You see these charges on your bill as Snowflake credits.