Just back and as a rought guide here are the prices that we found. Hopefully this will give you an idea of how much to take. The prices are a guide as some places will be cheaper/more expensive
Beer typically 4/ 5 lira, Buffalo bar doing it for 2.5 lira
local spirit and mixer 7 lira
soft drink 3/4 lira
set meal chicken dish, 17/20 lira
set meal steak dish 24/27 lira
litre bottle of coke from Tansas 1.60 lira
can of coke etc, 1.30 lira
small water 0.5 lira
bread from bakery 0.75 lira
water taxi to Marmaris 10 lira
sunbeds at beach 2.5 lira
chicken kebab at lunchtime 5 lira
pizza 10 lira
pide at luchtime 5 lira
English breakfast 5/7 lira
Vegetables like tomatoes peppers etc very very cheap
cappuchino, 4/5 lira
boat trips 20 lira
AI boat trip 30 lira
Jeep safari 30 lira

if you dont go for a set menu or none is available chicken dish is arounf 15/18 lira. Steaks are fairly expensive now, expect to pay anything from 25 lira to about 32 lira, in places like Wayside, Loveboat, Waterfall Bonjour etc