If the motherboard is bad beyond repairs, ask your repairer to extract the storage chip (eMMC) from the bad motherboard and look for a good card reader to extract the data ( if it's iPhone or higher version android phone) hev would need a good specialist with forensic skills to decrypt the data because most advanced phones encrypt their Data for security reasons.
It's going to cost him some money but if those data/ coins are worth it why not.
The repairer would have given him the advise. Or maybe he can take it to a different repairer.
This is true, he can try that. Pi of that amount should worth around $65 right now. But it is not as easy as you think. There are times that the data may not be recovered but not bad to try it. Have you done it before? I have seen someone fall into this problem before and nothing good came out from it.
It is worth knowing that mobile phones make use of UFS or eMMC, although this is not what we are discussing.
About the person that lost $1000, that is more difficult to retrieve. Probably the wallet did not backup the seed phrase on his phone. I mean as a file and he did not backup the seed phrase there too. This would likely be a wasted effort if trying to retrieve data on his phone.