The ever popular "it depends" is the best I can do. How are you doing your query, is it indexed (and can the query use them), what kind of hardware are you running, etc? Way more questions than answers, but I'd guess you are looking at about 3 seconds if you do it right.
If your queries are taking several seconds, then almost certainly you are doing full-table scans. Or you may be using subqueries that are being executed hundreds or thousands of times.
The EXPLAIN verb is useful for showing you the "execution plan" that has been derived from your query. The execution-plan is the actual 'program' that is executed by the DBMS to produce the results you seek. If the operation is going to be expensive, you'll see it right there.