Hi aiming56,
Even though Tahiti offers tropical weather year-round, the cheapest time for
Tahiti vacations is during the low season, that is from January to March (but it's hot). You can find cheap airfares, specials on
crusies and hotels offer packages with extra nights free. Peak season is from June-October when the rates will be higher, so if you are looking for reasonable rates, fewer tourists with good weather then visit from April to May.
We had our 3 weeks Tahiti vacation at
Bora Bora last April and it was wonderful. Really Bora Bora is a stunning island with exotic beaches, but the rates are little expensive. We stayed at the Novotel Bora Bora Beach resort which is one of the affordable hotels in Bora Bora and paid $138/ night. We had a buffet and it was around 25$ per person. The hotel we stayed was located very near to the
Tahiti beach, so we felt very comfortable for beach access and had more fun in our Tahiti vacation. Hope this helps and have a nice vacation in Tahiti!