How many SELECT/UPDATE/INSERT Operations can you run on a 4 core / 8 GB RAM server?
The maths behind it is far more complex than you seem to be implying.

Sub-selects count as queries in their own right, so a query with 3 sub-selects counts as 4 queries.

Size of the data matters as does indexing and indexability of every query.

If a query is returning 100,000 rows, it'll be orders of magnitude slower than a query returning 1 row.

If a query needs to check 1M rows to compute the result, it'll be slow regardless of the fact that it returns 1 row.

The "unit" of complexity is not a query. The CPU in question might get you 10,000 queries per second of one query on one data set, but 0.001 queries per second of another query on the same data set or 0.00001 qps of the same query on a different data set.

There is almost no limit on how computationally complex "a query" can be.