How much is a 4d 3n trip to taipei is going to cost me?

It's difficult to present a valid price without any information about where you will be flying from and what type of accomodations, food, and shopping you desire. The figure could go anywhere from US$500 to US$100,000+. Please add some details concerning these aspects of your travel plans, and I will return to this question to lend you assistance.

Thank you.

Dont worry too much about food (unless you want to only eat the expensive stuff) because its abundant and inexpensive. Shopping is not going to cost a lot like some other big cities, but since its Taipei, prices are usually a little higher than other towns in Taiwan. Its hard to say about your flight tickets and accommodations because you dont say where you are departing from, how good of an accommodation you want and when you are going (travel period) Prices can vary based on the dates.

Taipei,Taiwan is great to visit it, Taipei 101 is very popular around Taiwan, if you wanna visit there, you must be search out the website of Taiwan's travel agencies, they'll tell you what to do, then, why do I say that Taipei 101 is more fun to take a trip in Taiwan, because of Taipei is a capital city in Taiwan, Taipei 101 is a tall tower in Taipei, if you still have free time that I have some suggestions to you,
Taipei→Taichung→Kaohsiung, all of these cities are more development modern cities in Taiwan, if you don't know how to get there, may you can take high-speed rail, it's more convenient to visit there!!
Remember Taiwan isn't part of China, because Taiwan is a free and beautiful country around the world!!