If I understand Peachy's post correctly, I think she means that it's those who over charge on p&p by massive amounts that cause the problems not just those who complain about it - so I don't think she was meaning you as in your instances you had every right to have a moan
and indeed complain.
For too long some sellers have been overcharging like the examples given in the op. Buyers do get annoyed over this and so eventually they get that don't want want to pay a penny more than the stamp (or even in some cases complain even if they pay just stamp price) Ebay in their wisdom provided ways for buyers to express their annoyance eg the star system, and this has had an effect even on the sellers who don't overcharge on P&P.
The star system is flawed. When a buyer is asked if they are happy about the p&p charge they think "heck no I paid £5" - they don't take into consideration that it actually cost the seller £5 - so they mark the stars down. Too many low stars causes selling restrictions, and this can have a massive effect on a business.
the star system wouldn't have been introduced if buyers weren't complaining about overcharging and buyers wouldn't have complained if some sellers didn't overcharge in the first place.
I have had this discussion on here before where some mumsnetters thought it was ok to 'make a few pounds on the p&P'. And, as I have done here I explained the knock on effect of such a practise. I ended up being called all sorts of names and the state of my mind was questioned 
Back in the good old days of ebay, a seller could charge the correct amount of p&p ie the stamp price plus enough to cover packaging and everyone was happy. But then too many came along who thought it was a great idea to profit from the p&p and it was all ruined.
I now use free p&P on everything, just so that my stars don't go down. This does of course mean I pay higher fees. It does annoy me when I see or hear of those like the ones in op because it is those who have forced me into this corner. So moan away giggly! I shall join you :)