What the jewelers told you may actually be true.
A jewelry store has no economy of scale when purchasing pearls, Tahitian or otherwise. There are several different ways people in the industry purchase. They may buy on memo or consignment, or they may purchase the pearls outright. A jewelry store would buy their merchandise "by selection." This is the most expensive way to buy pearls, even if you are buying direct from a producer or a processor. But it's completely necessary for an operation that doesn't have the ability to move a massive amount of inventory.
When a larger buyer selects pearls, the pearls are purchased in lots - without selection. They can be graded lots or mixed lots. To give you an idea of the difference in cost, a full bag of Tahitian pearls that are graded (all the same grade) and not mixed in color could be $50 per pearl. If a buyer wants to buy "by selection," the price could easily be $100 to $150 per pearl. But in order to buy the lot, the buyer has to be able to move 100+ pearls of the same size, grade and relative color.
The next way to purchase is by mixed lot. A mixed lot can be mixed size, mixed quality, mixed color, or a combination of all. Mixed lots are the least expensive way to purchase Tahitians, but they are also the most difficult to work with. Well, the mixed size isn't that difficult, but the others are. We most often buy completely mixed lots that would range from A to C. We've purchased two so far this year - one lot in 8-10 mm and another in 11 up. Everything A/B and below goes into strands and everything A or top gem stays out for earrings, pendants, loose pearls and gem strands when needed. The 8-10 mm lot yielded about 300 strands, while the 11 up lot netted just over a 100. Our demands for A grade is higher than what we were able to pull from the mixed lots, so in February we purchased a mixed-size lot of 4000 8-10 mm, medium dark, A grade rounds. Next week we are doing the same thing for an 11 to 14 mm round lot.
What I'm getting at is that the jeweler may very well be paying $200+ for a single 10-11 mm pearl. It might not even be a top quality pearl. With Tahitians you've got light, medium light, medium dark and dark, followed by mixed color, separated green color, "special" colors and peacock. Each is more expensive as singles or as lots as your progress.