Thanks for the sarcasm, but the true answer is zero.
The purpose of mining is that you reward miners for making a valuable job.
If the mobile miner does not mine at all, then his work has no value, and the ETC coins they get as reward are worth zero.
Not true, because they can be mined on a pc!
I know there is real mining with PCs, and these mined coins indeed could have some value.
But I was talking about the free coins given to the mobile "miners". These coins must have zero value.
Either because the amount of free coins is insignificant (and, therefore, their value is practically zero), or otherwise they will cause the real mined coins to drop their value down to zero.