With orders of $25 or more, Amazon offers Prime members the Cooler Master Thermal Paste
, model no. HTK-002-U1, for $1.78
with free shipping
. (Non-members can spend $35 to bag free shipping.) That's the lowest total price we could find by $2. It purports to resist temperatures up to 350°F and is suitable for use with CPUs, chipsets on mainboards, and VGA cards to increase conductivity.
Note that this item is part of Amazon's "Add-on program" and can only be purchased with an order of $25 or more.