This depends upon which side of the desk you sit. I know prices vary tremendously, but from a healthcare provider's perspective the expenditure is as follows:
Provision of room - capital cost, business rates, heating and lighting. A charge of £30 to £40 an hour in practice has little profit
Staff costs - you have to have one other person. A qualified person such as a nurse FTE is £27 an hour including employer's costs
ECG. If amortised purely for this work the equipment itself would be £7 per patient if used 4-5 times a day five days a week
Audiogram. On same basis £12 but fewer candidates need an audiogram so you may have to double this
Training and software and computer capability for CAA probably £5 per candidate. I am not an AME and stand to be corrected on this one
Professional indemnity - I am hearing scary stories but allow £10 per examination
Other insurances £2
Salary - variable but to be the same as a bog standard GP £54 assuming an hour per examination allowing for reports and ongoing correspondence and communications
So about £157 per hour even if you can get one candidate every hour five days a week. Of course many AMEs are GPs who use the practice nurse, practice ECG and practice audiogram and lump in their costs which is all above board, but were they to step back and really consider whether the work is worth the extra hassle I dare say many might think again. These high costs are fine for employed line pilots whose employers pick up the tab but for recreational PPLs it is a lot of money and sadly both doctor and pilot walk away discontent financially.