In any larger battle, any variation in receiver/emitter will always come under some form of scrutiny, especially if those tanks enjoy any measure of success above the norm (skill notwithstanding). Tamiya remains the standard by which IR emission and reception performance is judged I think ausf found out how vulnerable his T34 was with its hull mounted quad-directional receiver setup was during the last NEAD battle.
As far as I know, for the array of aftermarket pretenders, only the Impact battle unit comes close to the Tamiya apple in terms of specification and performance (of having the right dimensions, prism and fins).
The current price spike of Tamiya battle units is just classic demand-and-supply economics at work - once the usual trusted-and/or-cheap sources are exhausted (like stellamodels, AAF Tank Museum), the market moves toward more expensive options to fulfill their needs. One of the guys in Singapore actually purchased a battle unit from Axels Modellbau in Germany simply because they had it in stock and he needed one to get in the action.
Given the scale of Tamiya's operation, and the small volume of TBU demand, it would not surprise me that they only periodically run their TBU production line for a limited number of units before moving to something else. So its a matter of time that they start producing again, or, if they are ending this item's production, it means that a TBU V.2 is in the works - they had just launched the
JS-2 recently and it would surprise me if they abandoned support for a new model in their flagship line so soon.
"Patience, grasshopper......"