Locksmith taking advantage of a senior citizen

Yes it's all well and good to blame the locksmith, but it's an age old case of
"You get what you pay for".

If your friend had put some thought into the real dollar value of his tools and his shop, he would have a decent deadlock installed, with a commercial knobset underneath it.

But obviously he wanted to get out of it cheaply, and as a result he got a cheap job.