There are cultured pearls, which still can be somewhat expensive but not as much as the real deal, and there are all sorts of faux pearls and glass pearls available at every affordable prices.
When buying pearl necklaces, one thing to look for is hand knotting between each pearl. This gives the finished necklace a more authentic look, since real pearl necklaces are hand knotted, and it also gives the advantage of making your pearls stay intact in the event that the silk holding them does eventually break.
Another thing to look for is an interesting clasp. Most pearl necklaces are very simple and a fancy clasp will jazz them up just a touch. Also, don't just settle for white or cream. Pearls come in a wide range of colors and hues.
This stunning pink glass pearl necklace from my Vintage Jewelry Lane store is just exquisite. It features large 20mm pink glass pearls which are hand knotted between each pearl and end in a fancy clasp with clear diamante rhinestones. Perfect for both day and night- it has a very affordable price tag of $59.99 and comes in a lovely white satin lined display case and is perfect for gift giving.