Last time I checked the price for EV code signing certificate was around 350-400$. But obtaining the EV certificate is not the only obstacle; actually using their HCK software to produce a EV-signed tested submission package is a good exercise in tolerance towards Redmond. The system requirements are rather high, they demand a physical machine for the controller component, one Windows test machine for each target version (so to support a full range of only desktop OSes a total of 8 test instances are required: win7, 8, 8.1, 10, both 32-bit and 64-bit, plus the server instances if the driver is to run on server systems).
The test process itself occasionally fails for no apparent reason (e.g. test machine reboots) even for user-space print drivers. Some tests are mandatory, others can be excluded and it takes enormous amount of time and nerves to find out which ones (via some vague posts in forums), to produce a signed hck package which can be submitted to whql labs.