Chipped up John

Hi folks, I'm new here and hopefully someone can answer a question.. I'm looking at buying a 1/24 scale Stuka kit.. Amazon do an Airfix kit for £30.. However, on Ebay private sellers are asking around £100 for unbuilt kits that were manufactured in the 1970's.. What's the reason/s ? Different kit or is it just something collector pedantic like the differnt cover illustration ? Are today's kits okay ?