Hi anniesron!
Microsoft sets the price for this points. The most retailers earn from them are the discounts that Microsoft gives to its retailers. You can't buy them wholesale elsewhere. If you do find somebody claiming to sell them to you wholesale, my advice is to run away...FAST!
Microsoft is well known not only for the software and other products they produce, but also for the tight reign on their copy rights. Xbox Live Gold/Points is a gold mine for them and one of the best strategy to keep prices high on a hot commodity is to be in full control of its distribution. Sure, Walmart, Costco and other big retailer chain names can offer a discount for them here and there, but I am sure that there is a contract that exist between them and Microsoft that clearly states how low they can sell the product.
If you really want to sell them, try contacting Microsoft direct and ask if they accept application for resellers. That is the only way you can be assured that what you are selling is the real deal. :-)