chore: When sorting the prices of instance types, prioritize newer g…

…eneration

    instances over older when the are the same price

    chore: When comparing the cost of spot instances account on-demand instances,
    take into account a 28% compute savings plan discount

pkg/providers/instance/instance.go

@@ -406,7 +406,9 @@ func orderInstanceTypesByPrice(instanceTypes []*cloudprovider.InstanceType, requ
 			jPrice = instanceTypes[j].Offerings.Available().Requirements(requirements).Cheapest().Price
 		}
 		if iPrice == jPrice {
-			return instanceTypes[i].Name < instanceTypes[j].Name
+			// sort newer generation instance types before old when the price is the same
+			// e.g.  c6i.large ( $0.085 ) before c5.large ( $0.085 )
+			return instanceTypes[i].Name > instanceTypes[j].Name
 		}
 		return iPrice < jPrice
 	})
@@ -473,7 +475,12 @@ func filterUnwantedSpot(instanceTypes []*cloudprovider.InstanceType) []*cloudpro
 		if len(available) == 0 {
 			return false
 		}
-		return available.Cheapest().Price <= cheapestOnDemand
+		cheapest := available.Cheapest()
+		if cheapest.CapacityType == v1alpha5.CapacityTypeOnDemand {
+			return cheapest.Price <= cheapestOnDemand
+		}
+		// if spot, compare to 28% Savings Plan discount
+		return cheapest.Price <= cheapestOnDemand * 0.72
 	})
 	return instanceTypes
 }