IMO you were reasonable with your pricing, and ÂŁ180 is not bad for a day rate, depending on your location in the country.
There are two types of customer who need (not want) an EICR,
Type 1, Landlords and sellers, these are not particularly bothered if you do a thorough job or not, in fact the less thorough the better as far as they are concerned, and this type of client just want, as E54 said, a piece of paper saying all is 'tickety boo', and price is probably the most important factor for something they don't want, but need, and see as a neccessary evil.
Type 2, the buyer, most sensible clients of this type will want a very thorough job doing, as after all it is their investment, and the price being of secondary importance, in fact the more thorough the better, as anything you 'flag up' can be used as a bargaining chip to get a price reduction etc.
As Electricians, we are faced with the same paperwork, and what should be (but often isn't) an impartial and professional assessment on the condition of the electrical installation, against two diametrically opposed reasons for the report.
Sadly in any industry there will always be an element of fast buck merchants, who will cut corners and (not always) prices, and who will bow to the clients agenda.