It is very difficult to predict when it comes to auction on Ebay.
For example, only a month ago, I won two auctions.
Child Whisper £98.99 (Although stated as 1st edition, I knew it wasn't- I had this in mind when bidding!)
http://www.ebay.co.uk/itm/Child-Whisper ... 7675.l2557" onclick="window.open(this.href);return false;
Silver & Gold £69.87
http://www.ebay.co.uk/itm/Silver-and-Go ... 7675.l2557" onclick="window.open(this.href);return false;
Out of 5 poetry books written by Enid Blyton, these two were the ones I hadn't got at that time. So I was willing to pay for quite a sum of money.
I was very anxious waiting for the auctions to end! I was expecting them to reach much higher bidding prices i.e. well beyond £100 to be sure judging by the prices of the other online listings being listed throughout the whole online markets. Just to give examples on Ebay:
Child Whisper
https://www.ebay.co.uk/sch/i.html?_from ... r&_sacat=0" onclick="window.open(this.href);return false;
Silver & Gold
https://www.ebay.co.uk/sch/i.html?_from ... d&_sacat=0" onclick="window.open(this.href);return false;
I consider myself very lucky. I live in Malaysia and the only way I could buy vintage Enid Blyton is via online market. I do not have the advantage of rummaging bookshops full of vintage Enid Blyton! So I have learned that the only way is to rummage this wide online markets to get the bargain. If I had concentrated on Ebay alone, I wouldn't have got the bargain!
And I have learned that most of the online prices are the true reflection of their scarcity(plus books condition) or the lack of it. I could not compare the price in 2017 with the price in 1990! However, sometimes, you would find the outrageous and absurd prices i.e. too high or too low, for that matter that set them apart from the other listings of the same title and edition.