I've been to quite a few fine dining establishments that had very generous portions. The best advice I can give is always ask the waiter in order to gauge how much you should be ordering. As long as the restaurant isn't run by total assholes, you'll get an honest answer. Waiters want to make you happy as their generous tips are largely powered by your enjoyment. Having a miss-portioned meal and paying a fortune doesn't encourage a reasonable tip.

You really need to ask the waiter before hand. Often times at fancier restaurants you aren't expected to just order and entree and be full, and yet that's what some patrons expect.

An example is high end Italian places will often have a pasta section at say 20-40/item and entree's 30-100's, and you think you can just order a pasta and have a good meal. Except you're really intended to order a couple appetizers, a pasta meal each and an entree. It's not them trying to take all your money, but it's what the normal clientele expect. It's also often what the food quality/prices demand.

If it's a truly good restaurant (and not just an expensive one), you shouldn't be coming away hungry.

I don't think I've ever seen a prix fixe/chef's selection menu that wasn't going to leave me absolutely stuffed. If you go somewhere and order a la carte and plan to spend "normal" nice restaurant prices (say, $30-40) sure you'll get a smaller size. But if you're spending like $70+, you'll almost always leave full. The one actually starred restaurant I went to, I skipped lunch and could still barely walk home it was so much food. 6-12 courses add up, even if they're small.

My wife and I have gone to In-N-Out after fancy dinners on a number of occasions.

Really depends on the appetite, and the restaurant.

It's a bit like an art museum. You can go get a ticket to the Hermitage, and you would probably need 3 full days to see every single thing in it.

For the same price, there might be some museum that shows only a few paintings.

Does that mean the bigger museum the better the value? Kind of? If the goal is to get an experience, there are many ways to experience some emotions (and in the restaurant's case flavours) that won't lead to thorough "satiation", but would still be novel.

Some museums are like that, and you'll want to go see an Avengers movie afterwards to satisfy your entertainment.

Some restaurants are like that, and you'll hit MacDonalds on teh way back.

But more often than not, Michelin-echelon restaurants will overwhelm you with a ton of tiny courses, by the end of which you will be fairly adequately stuffed.

The portion sizes usually factor in that you'll be ordering appetizers or multiple courses. But that jacks up the price a ton.