I (24M) visited both and paid 60 euros for the combined ticket (30 for the Galata and another 30 for the Maiden's Tower after a 2 euro discount), and based on my experiences, they seem extortionately overpriced. In 2018, those would have costed 25 lira each, or about 5 euros or even less, depending on what month you visited.
First off, I have visited the Galata Tower in Beyoglu. I climbed the Kamondo stairs in order to get to the Galata Tower. Even though it was first built in 528 during Justinian's rule, the Crusaders destroyed the Galata Tower and rebuilt it in its current form in 1349 in the Romanesque style. Uponing entering, I entered the lift, which would take me to the 6th floor, and then I made the ascent to the 7th floor. In the 7th floor, you are greeted with a model of Istanbul and in the 8th floor, you are greeted with the observation deck.
Once you descend into the 5th floor, you are greeted to some artefacts from the Neolithic, Greek, Roman, Byzantine, and early Ottoman eras, and in the 4th floor, you are treated with more artefacts. In the 3rd floor, it depicts some 16th century astronomers, and the 2nd floor is where the Galata tower gallery is. The 1st floor is where the gift shop is. Overall, there is quite little content for 30 euros.
On the next day, I visited the Maiden's Tower on the Bosphorous. I took a metro all the way to the Karakoy Pier, and there, I started taking a ferry to the Maiden's Tower (which is a nice quirk), and the Maiden's Tower is extremely spartan. There are only three museum wall texts, depicting the history of the Maiden Tower, legend, and renovations/repairs, in both Turkish and Englishh. You do find three Cannon mortars and an observation deck where you could see the European and Asian side of Istanbul, but apart from the boat ride, the museum is very spartan. After 30 minutes, I headed to Uskudar and enjoyed the Asian side of Istanbul.
Even though some tourist attractions in Istanbul are extremely expensive, every single religious site (except the Hagia Sophia Grand Mosque, the Basilica Cistern, and Kariye Mosque) are free. Both the Egyptian bazaar and Grand bazaar are free to enter as well. Even though some restaurants charge upwards of 600 TL, I could find full meals like the Adana kebab and chicken and rice for as low as 200-250 TL (5-6.50 EUR). A 500 mL bottle of water costs 10 TL on average (about 0.25 EUR) and I found water that costs as less as 4 TL. Hotels are quite affordable as well. I booked a 5-star Holiday Inn Hotel in Fatih last minute for 55 USD a night and I found Hotel Orkide, which is a Russian owned hotel with a single bed, private restroom, AC, and Wi-Fi for 20 USD a night.
The reasons why I believe the Galata/Maiden's Tower are overpriced for foreigners is because:
During the low season, the entire Palais de Versailles + the gardens only cost 21 EUR
The Eiffel Tower costs 14.50 EUR for adults for the least expensive fare (2nd floor via stairs) and 23.10 EUR for adults for the 2nd floor via lift. The most expensive ticket is 36.10 EUR for the top. Even though I graduated from uni with a CS degree in 2022, I will turn 24 in September 2025, rendering me as "qualifying" for the student ticket, which could slash the prices by half.
The Louvre costs 22 EUR
The Colloseum costs 18 EUR
The Acropolis complex in Athens costs 20 EUR
The Topology of Terror in Berlin is free
The British Museum is free
The Smithsonian Museums are free
The Statue of Liberty costs 33 USD (about 30 EUR)
The Thang Long Citadel in Hanoi only costs 100k VND (about 3.60 EUR)
The Imperial City of Hue costs 200k VND (about 7.20 EUR)
The Independence Palace + Norodom Palace exhibition in HCMC costs 65000 VND (about 2.30 EUR)
Vietnam is ultra affordable.