>>1474500240k is not more expensive than video or computer gaming.
It takes around a hundred dollars to start up (rules, some paints, glue, file, brushes, flock, dice). From then on, you can add an additional component for 30-50 dollars (or a smaller component for about 17 dollars) whenever you feel like.
This is akin to buying a console and getting a new game maybe once a month, depending how you feel.
As with video games, you can find always better bargains on the internet. You won't get minis for free on the internet like you can with video games, but I've got quite a few from just hanging out at a gaming store.
The disadvantage of 40k is that it requires genuine work to build an army. This means you will sit under a lamp for hours cutting, gluing, basing, and painting tiny plastic mans. If you cannot handle this prospect, don't waste your money. It's like wanting to play video games but not enjoying sitting on couches or chairs.
The advantage is that you will meet people, often interesting people, and spend several hours interacting with them in real life. You will also get better at the disadvantage above and, hopefully quickly, come to take pride in your ability.
So, 40k isn't more expensive than other timewasters. It is more demanding, and if you can't handle the demand, it is better that you not try. There's more than enough unpainted, mold lined, glue-melted armies sitting in people's closets gathering dust to testify to this.
