Fans, RAM, and drives... three things I am embarrassed to propose to 3300 customers due to Mitel markup.
The fans are industry standard 92mm (I think, maybe 80mm, but it's easy to search the part number of the fan itself) that are about $1 each, just have to swap the plug.
The RAM is literally a <$20 piece available from Crucial.
SSD's are <$50 for a replacement drive.