Google Apps and SPAM

It so happened that Google did not cope with SPAM on our domain. As you know, the SPAM folder is cleared once every 30 days. We have a mailbox info@ourdomain.ru, here are 2 sad screenshots from it:


and second:


While I see several options:
1. go to this box at least once a week and clear the spam folder. Unreliable.
2. Switch to the commercial version of Google Apps (the toad presses, in fact, in the domain of 24 boxes, you get $ 1200 per year).
It is a pity that in the settings it is not possible to set the period for cleaning the folder.
I am writing in a personal blog, I understand that not everyone is interested, but maybe someone will tell more acceptable options?
UPD : the person who works with the mailbox uses the email client. It comes through the web-interface only when the sender says “I sent you a letter”, but the letter did not reach. Sometimes such letters get into SPAM.
It just so happened that there were no incidents in the last month. Removing SPAM immediately through the filter is somewhat dangerous (as I said, sometimes the “correct” letters get there)
UPD2 : I came up with an idea that would help solve such problems, but, unfortunately, is too utopian. Idea: Google should not include the volume of the folder with SPAM in the total volume of the box. In the end, it will be fair, detached we can assume that Google makes money on our SPAM: the more SPAM, the better the filtering algorithms, and therefore the better the service.