Would it cost less to get iphone4 repaired than to buy a brand new one?

My brother gave me his hand me down iphone 4 and i've had it for about a semester. The front screen got cracked so i tried to fix it myself, i got some of the screws mixed around and it won't turn on.i've tried dfu mode and i tried to hook it to itunes and it says error 21. Would it cost less to just repair the front screen and the problem, or should i just buy a new one. (my mom really can't afford a new one) but they have some good deals at store. Help! Because i've got 80 dollars. I really want my phone by next week.

Of course getting it repaired costs less, but you should figure out what you need to repair. For a screen replacement part, it takes around $30, you can have a look.