I would also like to see Xenonauts on GOG.com. I would gladly buy it from GOG as well as the pre-order I already got.
The price tag shouldn't be a problem as I think every game negotiates it's own price. When they released The Withcer 2 on GOG.com it's pricetag was $39.99 I believe (or was it $32.99).
Anyhow, I think Chris will have a word regarding pricing of Xenonauts on GOG.com.
Also, many of the customers of GOG.com should be very interested in Xenonauts as the original X-COM is already a good old game and I believe many are visiting GOG.com too see if it's there. I know I did