We were married in Moorea (sister island to Tahiti) and have been 3 times. My wife's great uncle owns a small resort on Moorea. If you haven't booked everything let me know as the little resort is quite a treat. The bungalows are all little wood and thatch huts. Very traditional looking and very quiet. They also have full kitchens so you can save a bit on food costs then.
As for costs, yes, they are high but there are some less expensive places if you don't need to stay in above water bungalows. The market in Papeete has some less expensive food options and in the harbour they have basically food trucks. If you're focused just on restaurants it is high dollar for the most part.
Getting around, the bus system is pretty easy and inexpensive. Having a bit of French language ability goes a long way to making it easier to get around.
Let me know where you're staying and I'll give some more suggestions.
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