I bought an inspired-by Birkin for my 37 year old daughter a couple of years ago. I would not have considered buying her a Birkin, both for the cost and because if I were going to spend that kind of money, she would prefer something else - work on her house etc. She loves her bag - it was excellent quality (no, not Hermes, but still very good), and it has held up well as her daily work horse bag. I paid about $850 for it.
I have an inspired-by Constance. Again, I can't pay that much for a bag I would only use occasionally.
I also have two Kellys - one bought new at the boutique and a 1974 vintage one. I also have a Picotin that I bought at the FSH store in Jan.
Having said all this, I would never buy "tons" of inspired-by bags. I would much prefer to have one truly high quality Hermes bag and enjoy wearing it. To me, one buys an inspired-by bag only if the cost of Hermes is totally out of the question and will be so for many years to come, not just to have bags in every color.
I would NOT buy a "fake". "Inspired-by" and "fake" are two totally different things.