There are just so many things you're overlooking.
You buy a nice Bravo boat with 500 a side and you're basically running in a Chevrolet. That OL is a Porsche- with Porsche maintenance and prices.
Let's start at the prop nut- bend a blade on a Bravo prop- $300. On a six- $3,000. Twice a year maintenance on those sixes- ten gallons of merc lube. rebuilds- ship them to one of 5 or 6 people in the country any good at it. Check the BAM website on six parts- The refresh costs what a Bravo does.
In the engine compartment- Blower motors? Especially what appear to be old carbureted 500's with blowers stuck on? Grossly under-carbureted blowers? Looks like this thing got whatever was laying around stuck on it. Nonetheless, even if it runs OK and gets you a season, if you're sending this thing out to someone else to work on it, you're a short distance from being up to your eyeballs. You could be a year away from a bill of 25 to 30 grand- or more- to fresen the engines and drives. That'll set you back- or maybe keep you off the water for a season or so.
We could go on.
To my original comment- I'd suggest you focus on the big picture. The total cost of owning the boat. Unfortunately, you want what virtually everyone wants- a clean, well-maintained boat that runs respectable speeds with non-exotic hardware and maintains value. That's why 5-6 year old twin step Top Gun's cost what they do.
This is maybe the only universal truth in performance boating- the best time to sell a boat is at that point where it still looks and runs good, but is close to turning the corner. Boats- or anything else- will continue to look good and run well if they're getting attention paid to them. Thr trick is to move on while it all still looks good. And the smart guys do. The best person to sell this sort of boat to is an inexperienced guy that falls in love with the look and the seemingly low pricetag. We see them att the time on here the day they bring their gem home, posting "bought this- whaddaya' think?" Sometimes the replies they receive are photographs of the boat sitting semi-submerged. Oops- seller forgot to mention that. So you're doing the right thing so far in that respect.
I'd suggest you take what we're throwing at you and re-evaluate your list. Some of what I've posted here shows that there's alot more than "75 mph and a good deal" to be considered. And I'd think about your total annual budget for operating and consider what happens and how you'll pay for whatever breaks.
. I don't get the impression he's in position to absorb a major mechanical failure, after purchasing the boat, and securing insurance. This boat does have some nice parts, but they don't seem to be in very nice condition. If $75k is his number that he'd like to spend, and be BOATING all Summer, this is not the boat for him. It would however be a nice buy for someone ready to put a little love into it from the get go. 
