D
Had a similar experience this June/July in Majorca. There was 5 of us so booked a minbus. No problem with arrival the minibus was just for the 5 of us. When it came time to go home a minbus arrived at our hotel and it allready had 2 women on board. I argued with the driver about the fact we had paid for the entire minibus to ourselves, but got nowhere. Then the minibus proceeded to make another 3 collections on the way to the airport.
So if everyone on that bus paid for a taxi the company was raking it in. We complained to travelrepublic who we booked with but as per usual no reply from them. So yes it looks like they are scamming us.
We are away again in October (already booked with travelrepublic months ago) but this time only 2 of us, the taxi is booked form Girona to Llorett DeMar, never been there before.
Sounds like the booking agent was taking the pish...
Use google to research the local tariffs and extras, then use google maps to work out distance, add %10 for good measure. This way you'll know roughly what to pay. Grab a cab from the airport, agreeing the price first (which you already know). When it comes to home time, get the hotel to call a cab for you, allow plenty of time though as last minute taxis have lower odds than the lottery.
Even if there are only 3 or 4 of you make sure that you get a car that is large enough for the luggage. If you need an estate car or people carrier because you've got golf clubs etc then be prepared to pay extra, although this shouldn't be a surprise because the official tariffs should include all the variations.
If you've had a few bevvies, be polite. Calling the driver a 'disgusting can't' ,as happened to me on Saturday, is guaranteed to leave you stranded. Remember it only takes a couple of phonecalls and you'll not be able to get a cab again in any given town or resort.
If you do feel aggrieved, for any reason, always take a card from the driver, along with their badge number, taxi plate number, reg and description. If you get into a licensed taxi or prebooked car, always pay, a criminal record is not worth the fare. If an unlicensed car picks you up, go wherever you need to. When you arrive, just get out and walk away. They cannot legally ask you for money. Just remember that they and you are not insured.