Personally, I have owned (and designed/produced) many suits over the years. The real difference I think between cheaper and more expensive suits is the fitment. More expensive suits are going to be more comfortable and not as baggy most likely, with a better tailored fit off-the-shelf.
That being said, the cheaper models by good brands like Sparco or OMP fit very nicely, and if I were going for an off-the-shelf suit, I would probably pick up something like a Sparco Kerb ($279) or X-Light ($575). I’ve owned a couple X-Light suits over the years and really like how comfortable they are and how well they fit.
If I were going to blow $800 on a suit, I would go with something custom designed/fit rather than an off-the-shelf suit.