So how much did it really cost?

Chicago-Philadelphia-Budapest- Vienna-Athens-Santorini-Athens-Philadelphia-Chicago 

Ten Day American Airlines Flight- 760$ (However, my two friends booked in December and got a round-trip ticket for 555$, insane.) Know what you want, and book early. 

Ryan Air Flights- $230. Short flights within Europe with a helpful staff, just make sure to pack light, and if you're not that type of person, add a checked bag when you book! I took a standard hard shell carry on and it flew for free with me ( I paid extra for priority, around 7 euro which was unnecessary but nice.) However, if I had to of opened the extra zipper to enlarge it... 40 euro each way. 

Airbnb Budapest- 10 euro per night per person (3-night stay). Budapest is an amazing city and you cannot go wrong staying anywhere in the city center. 

Vienna- Round trip bus ticket from Budapest to Vienna- 20 US Dollars.

Athens Hostel- Students & Travelers Inn. Perfect Location. About 20 euro per person per night. This is the perfect hostel to be close to good food, good shopping, the ancient ruins and a good nightlife. The rooms themselves are very small and beds are uncomfortable but I would not change my stay. (3-night stay)

Santorini Hostel - Markakis Studios in Fira - STAY HERE. This hostel was nicer than a lot of hotels I have stayed in, United States or otherwise. Again, 20 euro per person per night. (3 night stay)

Grand Total: 150 Euro which today equals 173 Dollars. 

Notable Extras!

• Budapest- 
• Hop on Hop off Tour - I recommend because Budapest has a lot to see and everything is quite spread out. 20-25 Euro.
• Athens
• Acropolis is ten euro with a student ID and twenty euro without.
• Airport to city center- 10 euro each way by subway, 6 euro each way by bus, 3 with student ID
• Santorini
• Boat ride to the volcano, hot springs, lunch in Thirisa about 25 Euro.  
• Cable Car to the boat ride, 6 euro each way (ripoff) you may also choose to walk or ride a donkey up.
• ATV Rental- a must to explore the island and beaches, 40 euro per ATV, split equals 20 a person plus a bit of gas money per day. 

Always remember to account for public transit, specifically from the airport. Taking a taxi 9 times out of 10 cost more, Europe is lacking in the Uber department. 

And of course...food. 

Europe is filled with great food and cheap coffee. A cappuccino and a cheese pie in Greece for breakfast does not have to cost more than four euro. You will see shops for a takeaway gyro under five euro. If you are sitting down a gyro will cost you around 8, a greek salad 6,7. 

Everyone is different, but saving on food and transportation can seriously cut down your costs.