My '01 R1100RT has averaged 40.195 mpg for the 4 weeks and 2100 miles I've ridden it. Looking at my mileage history since I started riding again the first of February I'm on track to ride about 18K miles this year.
If I could get 45 mpg on the K1600 over an 18K year it would save me about 50 gallons of gas. At the current price of $4.10 for premium unleaded that would be $205 per year.
Let's see... If I could get a K1600 out the door at $24,000, divide that by 205, it would take me only 117 years for the gas savings to pay for the motorcycle!
Seriously folks, even a 10 mpg difference in gas mileage wouldn't make enough difference in the cost of operation over the life of the bike to be the determining factor on whether to purchase.
For most of us, motorcycles are an emotional decision, rather than a purely logical one. If you like the way it rides and can afford it, then buy it. If not, then keep what you are riding now.
'74 Honda CB360, '77 Yamaha RD400, '83 Yamaha 650 Seca Turbo, '02 BMW K1200RS,
'01 BMW R1100RT