To be frank, $850 is a small price to pay when one may need to consider hundreds of thousands (or millions) of dollars of assets.
But if there is no need to spend that money, it is a huge price.
A simple situation can be done without a lawyer. The old man did one up with a computer based kit [installed on the computer, not web] and just to be safe he had a Lawyer do the once over and it was fine.
Really how hard is it to say everything goes 50/50 to both kids [widow he be], and some boiler plate about predeceased.
Or the house goes to X, account A goes to Y everything else goes to Z.
Granted if you have a horribly complicated asset set up, that is different but most don't.