https://youtu.be/xaT2hqHgLdY
Seems like he is getting approx 10w out of 10 modules.
The modules are now about 2usd each. So that makes it 2$/W.
The problem is you need 200 of them for anything usefull.
That is 4x4x200 cm^2
I am thinking one could make a warm air intake with them, make the engine scution cool the peltiers that are surrounded with a water jacket from the radiator (or engine oil if it is hotter)
If you build a box type of intake, with 2 on each side, that woould be 8 modules in the circumference. The length would be 1meter. A little bit long but achievable.