Depends on your data. If you have a link table that just contains two 4 byte integers, then yes, that's pretty significant overhead. Even if you have a few hundred bytes per row, it's still not entirely negligible.
Any overhead is generally considered irrelevant when you’re on a small database. For example, going from 50GB in a table to 75GB is 50% overhead, but easily handled in a time where you just pay for more GB on RDS.
That doesn’t hold true when working on multi-terabyte tables or databases when physical disk space in a chassis is actually a boundary you have to consider.
> Any overhead is generally considered irrelevant when you’re on a small database. For example, going from 50GB in a table to 75GB is 50% overhead, but easily handled in a time where you just pay for more GB on RDS.
Often disk-space is less the issue, and it's more about whether things can fit in memory or not...