Tome and Codex cost

I have been making all the research items in equal amounts without using most of them and I have just noticed that Tomes now need 2 Manuscripts each and Codex need 2 Tomes per codex. Is this a bug due to the gold requirements going up for Manuscripts?

I can understand the other resources requirements going up slightly over time, but I think the Manuscript and Tome requirements should never go higher than 1, it just ends up requiring far too much time if 1 Codex suddenly needs 4 Manuscripts and 2 Tomes to produce (and maybe 9 manuscripts and 3 tomes later) :(

This is not a bug, it is designed that way. Why? Nobody knows

The progression charts for science are here -> http://www.settlersonlinewiki.eu/gui...tem-geologist/

It caps out at 3 tomes per codex, and 5 manuscripts per tome.