what price would be a good estimation for a trip to Europe?

Question

including tickets from LA, food, hotels, 4 train tickets that are $1000 each, and about $1000 for Souveniers.

Answer 1

It depends mostly on what kind of accommodation you are going to use and where in Europe you go to.
There are hostels that range in price from $ 10 to $ 50 per person per night. Hotels range from $ 25 to $ 400 per person per night.
Eating is the next consideration, if you cook your own meals, or eat in the cheapest places, you might be able to get by with $ 10 per person per day, but if you go to fancy restaurants you can easily pay $ 100 per person, excluding drinks and it is not hard to find more expensive places.

For your air tickets, do you fly budget in winter, or do you take a normal ticket in summer, or do you fly first class?
And you also forgot to mention for how long you travel.

You will have to research a bit more yourself, as nobody but you can say what kind of accommodation, meals and airfare you prefer.

The average tourist in Amsterdam seems to spend $ 275 a day, but I have also heard from people going on an extreme tight budget of $30 a day, (spending nothing on travel by hitch hiking and sleeping in the house of people he had met while traveling most of the time.)