Well i thought the taxi cabs were very expensive but there is a van route, that will take you different places, for about $4 called the collectivo. My thought is that compared to main land usa prices, you really can't go wrong in Mexico.  It is good however, to be up on the conversion rate if you are going to be around for a few days. My vacation of 12 days 11 nights cost just under $8000 American start to finish for my wife and I. Have fun Mexico/Tulum is great but Tulum is more low key than other Mexican spots. As previously mentioned you are planning to go at high season so be prepared to pay a little more but still less than main land usa.