I've heard on the grape vine that Importers of tyres have two different compound levels available for the exact same tyre i.e Goodyear F1 GSD3 one will be a higher spec compound at a higher price if you get my picture..
Apparantly the manufacturers create these two different grade levels depending on the country they are designated for...
I have no idea how true this is, but i heard this from A tyre dealer who uses a broker who offers both levels. Like I said could be total B*llox but could also make sense.
I shopped around massively, both locally and online for ages and found many places which were cheaper than local tyre places but all seemed to be around 20% cheaper and no less.
But the odd company like the link you posted is massively cheaper, makes me wonder why...
Would be nice to find out the absolute truth, as we could all save a fortune!
Hornet