Ok here's a good question for all of you, I am sure we will get a lot of different answers... I may be wrong though...

How much unique traffic per month would be considered a high traffic site?
1k
10k
100k
500k
1M

Totally depends on the niche...

A site about crocheting that's "high traffic" might get 30K a month (I have no idea how many people are really looking at crocheting each month, that's just an example, but there are some niches where you can take all the top spots and struggle to get 1K a day).

A high traffic porn tube site might get 15 million per month (some get way more).

Traffic is just e-penis... Profit is the only number that really counts, and it's usually determined by the quality of the traffic rather than the sheer volume.

sorry misread
so you mean UV?
I think 1M+ is a minium for a "high traffic site"