I fix my stuff, when I can, because I enjoy it. I don't sharpen my own mower blades because I've just never gotten the hang of it so I take them to a local hardware store that charges $5.00 (3 BPS) per blade. If I run across something else I can't do, I'll take it to a shop.
I'd say your price for basic service is pretty much on par with what would be charged here in the U.S. at most shops, at least here in the mid-west where I live.
Do you charge an additional fee for pick up and drop off?
Rotary Blades need to be balanced, you can get something for that off eBay ! Have a read up on how to do it, we all had to learn
As for pick ups it depend on how far away they are from me, within 5 miles free, also what it is a walk behind mower say £10 = $15 but a big ride-on could be as much as £30 = $45 as time is money and mucking about putting a big mower on my van is not making me any money I am losing it.
People think we put all that money we charge in are pocket! But we don't we have to pay for running a van, a workshop, heating the workshop , lighting it, tools, buying parts that can takes up lots of time that we don't charge for, and all the other costs to running a business, then and only then do we get some money for us!
Most of the time the people we employ take home more money the we do.