Some people have acused me of making the wayland book free because it wasn't selling, or doesn't "have value".

First of all, fuck those people.

Second of all:

select date_trunc('month', created) mo, count(*) from purchases where price > 0 group by mo order by mo desc;
mo | count
---------------------+-------
2020-05-01 00:00:00 | 3
2020-04-01 00:00:00 | 26
2020-03-01 00:00:00 | 29
2020-02-01 00:00:00 | 20
2020-01-01 00:00:00 | 30
2019-12-01 00:00:00 | 25
2019-11-01 00:00:00 | 19
2019-10-01 00:00:00 | 47
2019-09-01 00:00:00 | 75
(9 rows)