Last week I realised that I did not reserve enough of my time to tend to the garden. I then decided to request the services of a gentleman to assist with the garden.

During our negotiations I had a moment when I realised how selfish pricing can be.

Firstly time is equal. If I spent an hour in the garden, it would be the same as spending and hour in the garden for him.
It is however clear to me that the value of our hours in the garden, are not the same. He would probably be more efficient at gardening than me.

This means I need to place a value on the garden. Is a well maintained garden valuable to me and what compensation is suitable for getting it to that state?

It stopped being about time, it became about the garden.
As overly simplified as it sounds, Give what would satisfy you if you had to do the work!