Hotels/BnBs? Warsaw, Krakow, Treblinka, Izbica

We had a great stay at the Metropolitan Hotel in Krakow. Large room, amazing breakfast and easy walking distance to the Jewish Quarter. Highly recommend! http://www.hotelmetropolitan.pl/

Have you tried searching on www.booking.com? There are lots of reviews there, and you can easily filter on your price range. I assume you can get to Treblinka from Warsaw, so no additional hotel needed there. I would stay in Zamość nearby Izbica, it's worth seeing (the Old City is a UNESCO Heritage Site).

Airbnb prices for Krakow are fairly reasonable depending on the time. For example our airbnb in Krakow is around $140 for 4 nights. That is for 3 people in a private apartment in January 2018.

I've always stayed at the B&B La Fontaine in Krakow. The main location is right on the Main Square, and there's at least one Annex location that's a block or two off the Square. It was nice and convenient, with a good breakfast. http://www.bblafontaine.com/en/
I second the suggestion to stay in Zamość, but will also offer up Lublin as a suggestion. It looks like it's about an hour's drive from Izbica, but Lublin is a wonderful town. I spent three summers there and love it. It's also the location of Majdanek. The first summer I was there, I simply took a bus outside of town and looked around by myself. The second time, the program offered a tour of the camp. Either way, it's a very moving experience. I found Auschwitz, especially Auschwitz I, to feel like a museum, whereas Majdanek had a very eerie, somber feel. You'll also find there the memorial to the 43000 Jews who were murdered in the "Harvest Festival" in November of 1943, as the Nazis were trying to "clear" the Lublin region of Jews. You probably already have this, but just in case, Ordinary Men: Reserve Police Battalion 101 and the Final Solution, by Christopher Browning, details what occurred in the region during the Holocaust and I believe includes information specifically about the clearing of Izbica Ghetto.

In Krakow I stayed at Grodzka 4 apartments (now listed as Krakow For You Apartments on booking.com). Great location in old town, just steps from the main square and lots of restaurants and convenient for the tour companies going to Auschwitz/Birkenau, if that's how you're getting there, or also for the train station. Very nice studio apartment good for 2 people at about $80/night. I loved it.

Thank you for all the suggestions. The Metropolitan in Warsaw is over our budget - any other suggestions for a hotel in Warsaw?

Keep in mind I was a poor grad student at the time, so these might not be to everyone's liking, BUT -
All the times I stayed in Warsaw, save one, I stayed at the Hotel Mazowiecki http://www.hotelewam.pl/636-hotel-mazowiecki-warszawa.html It's no frills, but clean and the staff was always extremely pleasant and helpful. It's a few blocks from Nowy Świat, which turns in Krakowskie Przedmieście, AKA the main drag to Warsaw's Old Town. It's also possible to walk to and from the train station, although it will depend on the weather/how much luggage you have/are you willing to walk about 20 minutes. It looks like it's about $50/night for a double. There are some bars/clubs on the street that can go into the night, but if you ask for a back room you should be fine. I also stayed once at the New World Hostel, also on Nowy Świat. It looks like they own and operate the Chmielna Guest House, which seems to be nice and cheap. http://www.chmielnabb.pl/en_GB/index.html

Which city is the most expensive in Poland?

We stayed at Between Us BnB in Warsaw, great location, fantastic breakfast. The standard room would be in your budget range. We stayed in the bigger room because I couldn't book early enough. In Krakow, we stayed at La Fontaine. Be sure to verify that breakfast is included with this BnB but it definitely is in your budget. Great location and breakfast, a little loud at night, wear earplugs!

I would advise restaurants in Krakow. Most of them are very beautiful and most importantly they have in their arsenal tasty dishes such as Starka salad, a chopped steak with herb butter and fries, vareniki and even vodka. You can choose from the list of restaurants that suit your taste: The 10 Best Restaurants in Krakow, Poland