If you’re committed to your yoga practise, and can see yourself doing it long into the future, then you have to be prepared to spend $50 or more.
There are exceptions of course, like the excellent budget yoga mat BalanceFrom GoYoga which boasts low cost and good craftsmanship.
The more you spend, the better quality the material may be which means various things for your yoga.
If you want a luxury mat that would look great in your living room, or one which effectively absorbs sweat during heavy sessions, then that comes at a greater cost.