Amalgam price from negociant will go higher with each sector we unlock, it was somewhere in the patchnotes. It was 10 when we were gearing blue, it's 40 when we're gearing epic, and will be more next unlock. It's not a glitch, it's by design.
The price of Amalgam will alter with each unlocked stage of the season, correlating with the prices of the Glyphs of unlocked qualities.
See it here :
Negociants Preview