I don’t blame you venting your legitimate anger on here.
And I am all in favour of freely available information – rational choice in a free market requires perfect information about alternatives – but before I named and shamed, I’d contact the seller and ask what happened and how about a refund of the difference between price charged and service delivered.
If you get a reasonable explanation (and even better the money back!) you will feel better and you can let us know. If you get short shrift, you will feel a little bit more annoyed but also morally justified when you share the reply here and tell us who it was.
As for why some companies offer max limit or free postage is a business choice and they may have higher volume which allows them to negotiate a deal with the carrier or they may absorb some of the cost to get volume sales or simply add the cost into their production cost when working out unit price.
I don’t mind paying postage cost plus a small extra for wrapping material if it us up front and clearly reflects the cost. £14.22 for a £2.95 service suggests gold plated packaging or something odd. I’d ask them.