Liz- Please be careful doing this. My husbands suitcase and clothing were destroyed by someone who did this. It got cold enough in the cargo bay that the soda began to freeze and expand breaking the seals on the bottles. Then when things warmed up again, it leaked all over the inside of their suitcase, and out of it. It dripped down onto DH's suitcase and leaked into it. The end result was not pretty, and cost us quite a bit of money and vaction time replacing much of his clothing. The airline denied responsibility, and wouldn't tell us who the people were who caused the mess, just what had happened. That carrier is now out of business.
As far as answering the question, I think it would be at least $15 each way. For that price, you'd be better off just picking things up in the shop at the hotel. Or take a bus to the Marketplace, then get a cab to Goodings, taht would probably only be $3-4 each way.
Anne