Free products or services

I know I had asked this before. But am not really understanding it.
When I offer a free services to my customers I offer it to generate referral business.
But I seem to be unable to offset the costs of these freebies and log them as costs. Each hour of free services would normally generated 11.5£ of income and it usually costs me around 8£ to provide that free hour.
Surely there must be a way to log these free services and be able to log them as marketing costs?

Don’t major companies do that?
Your help would be highly appreciated.

If you are paying a member of staff £8 per hour to provide the free services, then you will claiming the expense and not receiving any income in return, therefore the costs will be higher without additional income being received.

and if you are not paying anyone for doing these free services then nothing come in accounts. Accountancy does not recognise opportunity cost, its works on actual money value