Although I could share your fellings about differences in the advertised prices and the price stated there are many methods searching and finding the best price.

Besides a minimum requirement of buying some fares more than 30 days in advance i imagine that there is some limitation of how far in advance you could book it.

So th ebest way would be to check directly with date and class of travel e.g. for more than one/two/three months to get a feeling about the prices.

That would be my suggestion!