@cleanerlondon1
YANBU!
You need to ignore and block.
Reminds me of when I used to sell a lot on ebay. I sold a few posters, and they were £3.99. In addition, it was £2.00 for postage/shipping, (including cardboard tube,) and £3.50 for Europe, and £5.00 to outside Europe. I had checked the postage, and sorted the costs - including the packaging, and it was correct.
One woman (from America) bought a poster (before I had everything on buy-it-now,) and didn't pay for the item. After 3 or 4 days, I sent her a polite reminder that she needed to pay before I could post it. She emailed me to say 'you can fuck right off honey, if you think I am gonna pay more for the shipping than the poster cost!'
I said 'well you knew the postage and shipping costs when you bid on the poster.' (She was the only bidder, so got it for the £3.99.) She ignored me, she didn't pay, and she gave me a negative feedback 
I gave her one back (you could do that to buyers then but you can't now... ) I said 'terrible ebayer - do not deal with this person. Bids on item, refuses to pay, and leaves bad feedback for nothing.'
But yeah, If I thought something was a bit costly, I would moan under my breath and then move on. Messaging someone to say that is weird, and rude. I would have ignored tbh.
Keep charging what you do OP. And keep up the good work!
I find cleaners invaluable and very underrated.