Advisable number of foreign keys in a single table
Yes, ultimately FKs can affect performance. They will certainly affect insert/delete performance (more lookups), but you have the advantage of guaranteed data integrity. 

You should be more than happy to pay a high price for data integrity - a high performance database with inconsistent data is worse than useless - certainly not as much use as a database that's a bit slow but with consistent data.

Yah gets what yah pays for!