I was out at the airport today and copied down the exact fares now being charged by the airport (yellow) taxis to various places in Mazatlan. One thing has changed since I last checked. They now charge by zone on a sliding scale.
Taxi - up to 4 passengers $26 USD or $260 MXN
Shuttle - per person $6.50 USD or $65 MXN
Zone 2 - Everything north of the El Cid Marina Hotel up to Cerritos Point.
Taxi - $29 USD or $290 MXN
Shuttle - $7.50 USD or $73 MXN
Taxi - $35 USD or $350 MXN
Shuttle - $9 USD or $88 MXN
Zone 4 - Oceanica and Stone Island (La Isla de La Piedra)
Taxi - $44 USD or $440 MXN
Shuttle - $11 USD or $110 MXN (but I would bet that they won't sell you a shuttle ticket to Stone Island!)
These are the posted prices (and I think they are pre-printed on the ticket you get), so they can't legally charge any more.
The one thing that is VERY obvious is that they are giving a really BAD exchange rate. You should go to the ATM machine that is just behind where you wait in line at the departure check-in counters and get pesos before you buy your taxi or shuttle ticket. Especially if there is a group, you'll save some money.
That ATM machine is in a kind of a dumb location, it's arriving passengers that need it, not departing passengers.