A good source of pricing info is eBay or the classifieds on AT+.
I think what you are referring to as a subscription is more accurately called a one time fee to unlock the receiver to the desired level of accuracy. I see quite a few used 262 receivers that are unlocked to RTK for somewhere around the $3K mark. A used 900 MHZ corrections receiver can be bought for less than $1K.
Trimble receivers don't have a clue about heading until you start moving. They then calculate it by comparing where they currently are to where they used to be. Those calculations are done very frequently -- 10 Hz or so and are as accurate as your correction source and displayed to 3 decimals of a degree.
Pitch, roll, and yaw are done via a steering control box. The EZ-Steer controller contains two accelerometers and two solid state ring gyros that compute roll and yaw. The NAV II and EZ-Pilot controllers use three accelerometers and ring gyros to compute pitch, roll, and yaw.
As far as accuracy comparisons to cameras or lasers, I'd put my money on a good RTK system with a nearby base station. Light refracts and causes inaccuracies when temps and humidities are uneven over the ranges you are measuring.