Sorry if it is off-topic. If I may ask, why cost is so restrictive ($2!) ?
I ask because I can only think of cost being a matter, when something is mass produced. What can be possibly so mass produced, which involves remote sensing with bridge, instrumentation amplifier, AM modulator with preselectable frequency, lengthy cables and noisy environment and so on. Which already sounds like costly lab setup for some material science made in quantity of 3 for whole global market.
I also imagine that problem is possibly real, technical and challenging and obviously costly. Two industry magnates meet in a bar and after few drinks go into arguments about the problem. In heat of debate one of them exclaims, "I will freaking solve it with $1 solution, just watch". Next day the problem show up in forums