You can do it yourself. I've replaced the glass on an iPad, 2 different iPhones and i've replaced an iPhone battery. The only problem is getting the parts, check out eBay, Mercardo Libre and Aliexpress. I considered doing this kind of work for people but fear being responsible for damaging peoples beloved apple devices should things go pear shaped.
There are plenty of good step by step videos that show you how to do it on youtube.
The glass for the phones for around 10-15 dollars each and the replacement battery was about 4 dollars, all cheap stuff from hong kong. They usually send you all the tools you need as well.
I've seen people charge anywhere between 90-300 dollars including parts.