Whether you purchase Amsoil from Ron for $11 a quart, Castrol from O'Reillys for $10 a quart ($10.99 not on sale?) or any other major brand that you prefer, pure synthetic is little, if any, difference in price over synthetic blend.
Also, 10W-40 is only rated up to 104F
In the southwest USA, using 10W-50 is important for summer ambient. It performed well in my 2014 Honda CB1100, 2020 Ryker and now my 2022 Triumph.
I well remember Harley-Davidson dismissing pure synthetic, citing "bearing skate" as a concern...because H-D did not yet have their private label available.
If it is so slippery that a bearing won't turn, then how could a bearing develop flat spots?!? Just being sarcastic towards H-D, especially since they discontinued Sportster models that I liked.
May not be an issue for Spyders, but the Ryker, with CVT trans, is cruising at 6,000 to 7,000 RPMs.