My experience is that some machines are very easy on oil and you can go 4 to 6K between changes, but some, like my previous and current Can Am Spyder share oil and SHEAR like crazy. If I want to change oil every 2000 miles I can use Rotella T, Valvoline dino or even Castrol Blend, whereas synthetics such as Amsoil and Motul will take me to 3000-3500 miles. Add a quart, or better yet, two quarts of 20-50 to either dino or synthtic and add another 1000 to the normal change.
Cost may also be relative to what you're physically capable of. At 80+ years I find that getting down and greasy is more difficult than it was a few years ago.
Still, I'm not ready yet to pay the dealer $125 to do it. So, for me, I take convenience over cost (about $50)and go with synthetic out of necessity and change at 4K.
Otherwise, I'd go with Rotella T and 2K changes for about $15.
Bottom line from an old geezer: do whatever makes YOU feel good.