The stock Suzuki paper gaskets (left and right side engine covers, cylinder base gasket) have a line of sealant in critical places where they are apt to leak - aftermarket gaskets don't have it.

I always buy the stock gaskets.....especially for the bottom of the cylinder and the head gasket.  Those are really hard to replace if you get crappy aftermarket gaskets and they fail.

If you shop around you can usually find a Suzuki gasket set at a bit of a discount.  Bike Bandit often has 10% - 20% sales on OEM parts, and if you are an AMA member you can always get 10% off from them.  Also if you watch eBay you can occasionally catch a bargain.....I bought a new Suzuki head gasket for $ 17 a few weeks ago which is about half price.

The Suzuki gasket set has a list price of $ 140.55, the online price from my dealer is discounted to $ 133.55.  Bike Bandit has it for $ 122.30 with free shipping.

You can get an aftermarket set on eBay for as low as $ 49.95.  I have no idea about the quality.
http://www.ebay.com/itm/Complete-Top-Bottom-End-Gasket-Set-Kit-LS-650-P-Savag...

There are more expensive Vesrah sets available on eBay, and that company has been around for a long time.  I don't believe the sets that include the side case gaskets are any cheaper than the Suzuki sets.