Denis Warobiew is an honest dealer.
Pinball Universe has grown quite bit since its early days nearly 30 years ago, from the "mom and pop" period in Colorado as an exclusive side business.
Another of the businesses that did heavy reimportation of games from Europe back in the 2000s.
Those were a different time in the hobby.
His crew is fairly small though, and all his techs except one are college age for techs with limited experience outside late and modern pinball machines.
You do get what you pay for as long as you know what you want, and what to looking for overall.
He is not going to shyster you, if you are looking for something high end as a collector.
I may have bought 8 machines or so from him in 25 years, and sometimes he even has some really special gold nuggets from collector buy outs.
I still peruse the website periodically.
"Know you games, your prices, and conditions of what to look for in a game title. You are the researcher, not the seller."