We recommend the Maroon Tomtom Hotel. Our tour from Kazan came out cheap at the height of the season, we didn't even expect to see such a hotel.
This is not the first time in Istanbul, so there is something to compare it with. The room is small and compact, but everything you need is there: a hairdryer, a kettle, slippers, soap, towels, water was supplied every day. The air conditioner was working, it was +18 in April, and warm air was sometimes turned on at night. We cleaned every day. For 6 nights, the bed linen was changed 1 time. The windows overlooked the neighboring building, but that didn't bother us. There's a museum there, no people were seen. If you turned your head, you could see Istiklal Street. Reviews everywhere say that it's noisy at night because of the nightclub. We lived on the 5th floor, it was audible, but it didn't bother us to sleep. If you sleep soundly, it won't be a problem. We had the same set of food for breakfast every day, and we had enough. Not a buffet. There is tea, coffee, and water. There is always a person at the reception.
We walked past Galata Tower every day. The only thing was that it was hard to climb the hill every day.
Tram, metro, ferry are all nearby. Walking along Istiklal street takes 10-15 minutes.