Interesting to hear how you manage your business, Breadfruit, though it wouldn't work for me. If I put my rates up I would lose all my customers as there are a lot of people who have taken early retirement and offer gardening very cheap since they only need to top up their pension, not earn a living. And I'm single, so have no other income coming in! I had 7 amazing years before peri kicked in though, so I am very grateful for that time.
Apologies...have gone off topic 
Dorothy, I thought exactly the same as you. Its a mental trap!!! Some very successful gardeners told me to do this and it works beautifully! Also some retireds do not have the same overheads like young couples have, like huge mortgages, credit cards and loans, car leases or loans, fancy holidays etc.
Dont believe just because someone is retired they have no money. Yes some do but not all. And dont worry about the competition. The customers chose YOU over them.
Just find one new customer at the higher rate and then do this:
1. Make a list of all your customers, starting with the best customer at the top (best prompt payer, nice easy garden, distance etc.). And the worst customer at the bottom (the one you dont mind losing).
2. Then put your newest highest rate customer to the top of the list.
3. Tell your worst customer that you have to put up the rate (you can go even higher than the new customer).
4. If the worst customer says "NO", then say ok and walk away.
5. You have one new higher paying customer.
Then repeat the whole process again. Find a new customer paying higher rate and start with the next worse customer of yours.
Simples!