Significant edit about 40 minutes after this was posted to correct errors...
I'll take you up on the offer...
Airport GOING TO Calle 2 Norte/ 5 Ave. Norte (Hotel Plaza Cozumel)
Calle 2 Norte/ 5 Ave. Norte (Hotel Plaza Cozumel) GOING TO The MAGA Supermarket
I assume the return trip would be the same cost for both destinations?
Data based on the September 2016 tariffs, shown on @el-graduado 's page,
Taxi rates. A slightly easier to read version of the first two charts is available at
https://www.facebook.com/download/preview/1918069515090179. The calculations below assume a maximum of four passengers.
Airport
GOING TO Calle 2 Norte/ 5 Ave. Norte (Hotel Plaza Cozumel) - this is all on Chart 1. Since there is no official taxi stand at the airport and you're hailing a cab from the street, all that we need is the zone-to-zone fare. You'll catch the cab at the southwest corner of Avenida 8 de Octubre (65th) and Avenida Antonio Gonzales Fernandez (Airport Boulevard). On the chart we see that is the very corner of Zona 1. Calle 2 Norte & 5 Ave is also Zona 1. You can either look at the grid to find the Zona 1 to Zona 1 fare, or take note of the first comment on the right side, "Servicio en la misma zona".
$26 pesos - done! (I'd previously stated a trip from the airport to Zona 1 was 31 pesos - I mis-read the map and thought the pickup was in Zona 3.) If the taxista is assisting with luggage, a tip is appropriate.
Calle 2 Norte/ 5 Ave. Norte (Hotel Plaza Cozumel)
GOING TO The MEGA Supermarket - this would seem to be Zona 1 to Zona 1, but on Chart 2 at the top we see, "De los hoteles del pueblo al centro" -
$48 pesos.
Return trips - Mega is north of Avenida Andres Quintana Roo (11th), the southern end of Zona 1. So from Mega to the hotel is Zona 1 to Zona 1 (Chart 1), but we need to add $8 pesos, for the official taxi stand ("sitios"). This is shown on the right side as, "Del Muelle Fiscal y Supermercados" - total
$34 pesos.
From the hotel to the airport, on Chart 3 we see, "De los hoteles del centro al aeropuerto" -
$102 pesos.
I had originally calculated everything off Chart 1, thinking that was all that applied to in town trips. It wasn't until I saw @goproek 's follow-up post that I did a little more research and found the hotel and "to airport" surcharges. (I don't normally deal with those.) Apologies to anyone who saw the incorrect information!
Fares are typically rounded up to the nearest $5 pesos.