It's really not like that at all, or at least it shouldn't be. There's lots of examples of this but I'll give you one that's simple and relatable. You want to go to the Dominican for an all-inclusive week of fun and sun at a nice resort. The cost for a single person to go on a package trip is basically the same as it is for two people (at least as far as the hotel is concerned) because the premise of these things is double occupancy. In addition, if you're not a guest at the resort then you can't come on the grounds, so you can't bring local girls in, and for you to play you'd need to go offsite and get some crappy room every time you want to indulge in a nice local chica (if you know how to source the girls locally). The obvious answer is to invite the nice local chica (dominican) to come and stay with you. The extra cost is minimal for a second person and a local girl would be positively thrilled to come and stay at a high end resort with you just for the stay, but of course you being a gent you'll probably give her some extra as well. For the time you're there you have a partner in crime for any activities you do, company for quiet times and meals, and a fun partner in bed, in a closed community that's safe and fun. It's not sex only thing, but it's not a GF thing either, and it's definitely not a by-the-hour thing, but it's a very good, simple solution that improves your situation without significantly altering either your costs or your emotional expectations. There's bunches of things like this where taking someone with you makes sense. The operative part is from where do you find your partner and what is the expectation? You could take someone with you from here but why would you? Again this depends entirely on location and logistics. Different circumstances require different approaches and this is just a simple example, but hopefully you can see what I'm getting at.
