A few comments:

1. The views are limited to 5000 (by default), not really the list. This means a design including a folder structure is less subject to the limitation.
2. The performance impact is more determined by the usage of the list than its volume. Number of read or write operations, and ratio between writes and reads are very important.
3. The performance problem, if any, could impact the whole SQL DB, thus the whole Web app (or site collection), not only the list being accessed.
4. The performance impact also highly depends on your hardware capabilities (mainly SQL).
5. You can increase the 5000 limit from the Central Administration, per Web app.
6. You can completely remove the limitation on a per-list basis from PowerShell (use [SPList.EnableThrottling], https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.splist.enablethrottling.aspx)
7. In SP2016, the problem could be mitigated: http://blogs.technet.com/b/wbaer/archive/2015/08/27/navigating-list-view-thresholds-in-sharepoint-server-2016-it-preview.aspx
8. In practice, I've seen lists with 20000+ items working perfectly fine, if they are not used too often (a few users a few times per day). And if you only have a few of these lists.

A few comments:

1. The views are limited to 5000 (by default), not really the list. This means a design including a folder structure is less subject to the limitation.
2. The performance impact is more determined by the usage of the list than its volume. Number of read or write operations, and ratio between writes and reads are very important.
3. The performance problem, if any, could impact the whole SQL DB, thus the whole Web app (or site collection), not only the list being accessed.
4. The performance impact also highly depends on your hardware capabilities (mainly SQL).
5. You can increase the 5000 limit from the Central Administration, per Web app.
6. If your view is always sorted on the same column, you can set an index on it. This will greatly improve performances.
7. You can completely remove the limitation on a per-list basis from PowerShell (use [SPList.EnableThrottling], https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.splist.enablethrottling.aspx)
8. In SP2016, the problem could be mitigated: http://blogs.technet.com/b/wbaer/archive/2015/08/27/navigating-list-view-thresholds-in-sharepoint-server-2016-it-preview.aspx
9. In practice, I've seen lists with 20000+ items working perfectly fine, if they are not used too often (a few users a few times per day). And if you only have a few of these lists.