A high arch foot has a hard time on a concrete surface. Fatigue and lack of adequate shock absorption take it's toll, as you have discovered. I am not sure how stretching exercises would help you, but I don't think it will hurt. A custom orthotic is probably a good idea in your case. Having said that, you should be aware that, like eyeglasses, the cost can vary from doctor to doctor. If you feel that you need to "shop around" then call several other doctors and see what the fees are in your area. Remember you are paying for the expertise of the doctor as well. Generally this is a case fee that includes follow up as well, but you should ask your doctor and factor this into your decision.
People always think there is something better and cheaper on the Internet. If you would not consider buying eyeglasses on the internet without an evaluation, then you probably shouldn't expect to find a suitable orthotic either.