Can someone explain stroker kits

Ive built several strokers and I never had $5000 let alone $8000 in a motor. If your not going crazy and shop around you can get a kit and have it balanced and build the short block for under $2000. You dont have to buy heads or cam or anything else to make them work. I think when I had the 408 Magnum in my Dakota I had $3500 in the entire engine(and I thought that was expensive) Shop around.