Everyone has a former life. I once sold synthetic motor oil.
First of all, oil isn't expensive. If anything dino oil is getting that way relative to the premium stuff. Modern synthetic blends have everything you need and probably more.
The idea that our engines were never designed to run on synthetic oil is nonsense. They will, I know this for an absolute fact. They will also run OK on regular oil but you will need to change it more often.
My own car runs entirely on synthetic lubes; engine oil, power steering, trans and diff. Nothing leaks out and I change my engine oil every other year.
Our combine runs on semi synthetic 15 W 40 and has since it was new back in 1983. At 4,500 hours it uses a litre every 7- 10 hours but it holds 22 litres. I've changed oil 8 times over those years. With conventional oil it would have been 45 times - that's a lot of used oil!
If your engine leaks a lot of oil stick to the regular stuff.