Judging only by review score, anything under 9 is probably not worth it. I'd say 9,5 is where I lose interest.

I actually never consider reviews when choosing which game to buy.
I prefer to watch gameplay videos and check the game´s website to see if it catches my interest.
There are some games that got generally average or poor reviews that I tried and had lots of fun, like Doctor Lautrec (3ds) and ZombiU (WiiU), while some high-acclaimed games like GTA and CoD are not interesting to me at all.

Nonsense. 

Splatoon 2 is one of my favorite games this year, especially after all the free DLC that has released since launch. 

Apparently so. Especially those that only look at the Meta scores.

I base mine on personal research, friends, and general word of mouth. I'll still look at site reviews, but those hardly sway me as much, unless a game is bugged to hell, or it's a bad port.

Actually read the review first. A score from slant for example says nothing to me, so I have to actually read the article. No matter how garbage it is.

Review scores are impossible to trust if have great or no interest in a game. You're likely to buy or ignore them no matter what.

Sometimes games fall into the low 70s that I'm very interested in and still I get them. Normally it seems like if a game is in the less than 60 range, there's a good reason to avoid it.

If it's below the 70s range, it moves to "is there a demo to try first?" category. Some of my favorite games have been low 80s/upper 70s in terms of crititcal response. I can still enjoy a game with some deep flaws. That being said. If you're looking at a sub-70 score - I'm not paying $60 as the admission price.

Used baby! :)

EDIT: As an answer to your second question: anything 90+ takes me off of the fence and into Buy-Land. If I wasn't at least thinking about it before, I'm probably not going for it either way. Reviews have some sway, but I put personal interest in the type of games way ahead of that. 

As far as how much money I spend, yes. A game has to be pretty awful for me to not want it at all, though.

Why wouldn't they? If the average game review on a game you were looking forward to ends up at like 5 or less, then that usually means there's something significantly wrong with the game. 

It shouldn't, but it does. 

It's the same reason I lose interest if the average is less than a 7/10 on average. it's not that I think the game isn't worth playing, it's that I only have limited time to play games, and limited money in which to buy games. I tend to only buy and play games that I expect to like or love. "Mediocre" games tend to not get my attention, and almost all games that are considered good or great have average review scores of 7 or higher. 

So yeah, of course review scores will influence what I buy. While I have disposable income, I can't gamble on a game I'm not sure of, and review scores are a good way to help determine and control the flow of cash. 

Except Yooka-Laylee. That game was great despite the reviews being mediocre/poor. PEople were complaining about it being what it was, when what it was was intended to be exactly as it is. Ah well.