Is it scientifically harder to lose the last 10lbs?

The reason it's harder to lose "the last 10 lb" or any weight, really, when you're already at a healthy weight is because your calorie deficit is smaller. The smaller the deficit, the slower the loss.

At my highest weight, my TDEE with exercise 3 times per week was about 2350. I could lose 2 lb per week (1000 calorie deficit) by eating 1350 calories, which is a bit low, but not extreme as long as I was eating nutrient-rich foods. At my current weight, my TDEE with exercise 3 times per week is 1985. Eating the absolute bare minimum of 1200 calories (which I do not) creates a deficit of only 785 calories, or 1.57 pounds per week. When I get into last ten pounds territory, my TDEE with exercise 3 times per week will be 1900. Eating at 1200, I would only be able to lose 1.4 pounds per week.

And anyone who is exercising at all should be eating more than 1200 calories. So yes, it is physiologically more difficult to lose the last 10 pounds.

I think with me I get to a weight I feel good enough at and then stop doing what I need to get that last little be off.

Or is it psychological ?

probably, especially if the goal weight is somewhat arbitrary for example getting to 30% fat shouldn't be "scientifically harder" than getting to 25% but 15% might be A Different Thing (TM)

Totally psychological, considering we all have different goal weights and expectations of what our 'last 10 lbs' should be.

It just takes longer. Also, if you've been in a calories deficit for a long time, you'll GAIN once you start eating at maintenance and your body restores your glycogen levels and the water needed to store it in. I plan on losing about five pounds less than goal, so I'll level off where I want to be.

For me? Psychological. Most def.

Or is it psychological ?

YES

I have no science to back this up at all, but I really think the human body does not like to be super lean. I lost weight very easily until I hit a healthy BF% for my stats...once I hit the upper reaches of a healthy BF% things slowed down dramatically...it seems that I really have to be spot on in RE to my calories and what I'm eating to get below about 18% - 19% BF...going from 30% to 19% was a breeze.

You are all incorrect. The fitter you get, the more you need to eat. It isn't in your mind. I have been my ideal weight all my adult life, and to loose an extra inch of my waist was practically impossible. I did arobics 16 hours a week, and swimming three times a week, and I had a 31 inch waist, and I am 5'8. Measure yourself rather than using the scales.

I have been my ideal weight all my adult life, and to loose an extra inch of my waist was practically impossible.

Then, I humbly submit, you were doing it wrong.

What is this "ideal weight" you speak of? How did you arrive at it?

If it was so ideal, why were you trying to lose an inch off your waist?

Your body doesn't know that your goal is X pounds.

Also if you logg everything on MFP, you'll see some numbers will change i.e. for every 10Lb you loose, 5 kcal is subtracted for each activity. So, a few more minutes, is needed on the threadmill for example, than when you where 10Lb heavier.