A lot of factors to consider. Without writing a book and sticking to the basics. If you target the site properly and keep your bid levels at around .05 you should be able to get close to 1000 hits to the tour.
Without geo-filtering a large percentage of them may not be able to be processed. Unless of course you are using an engine that allows you to choose the countries etc. Lets not forget click fraud etc.
I would say out of $50 you might see 400-500 decent hits to the tour. How does the site convert? You could see 2 or more sales or none on that campaign. Its just to hard to tell.
Give it a shot and let us know the results
