What should I expect to pay for a NES console?

I had this back in the 80s. It was my second game. The Atari 2600 was the first. I gave it away to my nieces and have regretted it ever since. I had the Zelda game and it was my fav. I have ever played. Could not wait to get home from work to play.

30$

I'm ready to pay 50$ maximum, if the console is in perfect condition, with 2 original pads

It depends on what kind of condition you want it in. I bought a NES on Ebay for nearly $200, but I paid that high because it was important to me to make sure that I got one in excellent condition that looked almost like new. If you don't care about it being in excellent condition then you can get one for cheaper. The cheapest that working ones seem to go for on Ebay is about $30, but those typically won't be in that great of condition.

Boxed Nintendo NES in good condition is on eBay around 120 British pounds (around 180 USD). With box it is more valuable for collectors and the price will increese faster.

I'd say between $35-$55.

Get Retron 5 :) it's Full HD, ebay is full of cartridges with games :) perfect for gaming on modern TV, it cost $100-$150