Tourism is a wide term. There are different sub-businesses under the tourism business, which includes transportation arrangement, hotel booking site seeing. Not sure in which country you want to start the same.
However, there is an aggregator model available for the technology entrepreneurs. The costs of all these businesses would vary depending on the country you are starting the business, your focus area mentioned above and the employees you would require. I believe personally, that to start a tourism website the major expenditure is the cost of the developers and the testing professionals. Additionally, there are different themes available if you are using the wordpress as your content management system
There are several factors to consider before thinking of a single figure, because the amount of money you need will depend a lot on how it is created.
Perhaps the only relatively fixed value will be the hosting service of your website that can range from $15 per month.
Well let's continue a bit, if you have no experience designing and programming websites no doubt must hire a couple of extra hands to help you develop the concept and that's where the money really is because you will have to pay the costs of programming and development of the entire website, and there will be many factors related to the type of web you want, has if you have to couple session functions and users, how many layers, if you want it to be multi-language site son on. In short a lot of aspects that will not come cheap. Taking into account those factors I would say that would add between 1500-2000$.
Now if you know how to do all the work of design and programming or if you use a landing page preset can cost you around $600 plus the cost of hosting service.
Another option that could be adapted to your budget is using a domain in Wordpress with a template specialized in tourism, where you would only spend $400.
In the end all costs will depend on what option you choose to make your web site, and how you decide to launch it.