The implant fee is based on the type of implants the doctors uses. I would refer the patients to the the doctors who use the implants that are manufactured here in the USA (Keystone, Noble Biocare) and stay away from the doctors who use inexpensive Korean/Tawainee made implants. These inexpensive implants are fine.....the problem is it is impossible to find parts when the crowns or the abuttments fail. When the USA-made abuttments fail, the doctor can easily order the new ones and replace the broken ones.
IMHO, the biggest variable in the cost of the entire implant restoration isn't the implant(pretty much a fixed cost by each manufacturer) and isn't the crown itself(once again pretty much a standard cost per lab/material of choice), but the actual abutment. If the bone is favorable and the doc placing the implant can put it in a location that allows a stock abutment to be used, then the cost to the restorative doc(and usually the patient too) are less than if the bone and or placement location requires a lab fabricated custom abutment to be used. For example, if I'm restoring an implant with a stock abutment and crown, my lab cost for that restoration is usually in the $300-$325 range. If a custom abutment is required to restore that implant, then I've had lab fees as high as $800 (usually around $600) to complete that case.
Usually when discussing an implant restoration, doc's will break the cost down to the patient as 3 seperate fees, (the implant itself, the abutment, and the crown), and then be able to talk about the standard fee for the implant and the crown and what the "usual" fee if for both a stock abutment (if applicable) and a custom abutment, so the patient is aware BEFORE the case is started