It's a known issue from your own topic below.

www.joomlapolis.com/forum/153-professional-member-support/237493-cbsubs-php-notice-non-well-formed-numeric-value#297772

Quickfix as follows.

IN: components/com_comprofiler/plugin/user/plug_cbpaidsubscriptions/cbpaidsubscriptions.sysplug.php
ON: Line 20 - 21
FROM:TO:
It's however just a notice and won't hurt anything. Folks, don't obsess over a servers error log. It doesn't matter if its filled with billions of notices. They're just notices.

You shouldn't be logging or outputting notices on a production environment. Only bother with those on a development environment. They have little to no performance cost when it comes to the interpreter (PHP). In this case it has no cost what so ever as it's just complaining that a math operation is being ran on an integer with a string in it (e.g. 100m * 100), which previously (before PHP 7) was never an issue as the string character would just be ignored. The interpreter logs a notice about this now as it may be unexpected behavior when writing code.

CPU is EXPENSIVE, RAM is EVEN MORE EXPENSIVE

Don't really agree here. If anything hardware is cheaper than ever. I typically stick with using a VPS for hosting as you can reseller it, host multiple isolated installs easily, run private Git repo, etc... For example you can get a VPS with 60GB SSD, 4GB ram, 3000GB bandwidth, and 2 core CPU for $20/mo; that should be more than enough.

I have to do everything in my power to make sure that we have clean mean 'not a single electron wasted' code for our website. Constant drivel from mindless Chinese and Ukrainian hackerbots is already sapping our resources, so much so that when three or four of the brainless bots happen to randomly traverse us at the same time as say a MSNsearchbot, it pushes us right into swapfile, rendering our site unresponsive.

Bot traversal shouldn't be taking down your site unless it's a DDOS. Nor should a log file negatively impact your performance in any way unless it's riddle with errors, which will destroy performance (a notice is not an error; the interpreter did not fail like with an error). You may have some public facing URLs that are causing heavy operations like traversing all your users (e.g. a userlist with hundreds of thousands of users) that could be causing a hangup.

Ok, this is fixed in latest CBSubs build and CB build. There were 2 such issues in CBSubs and 1 in CB. All 3 fixed.