If you're concerned about pricing, you could get cloth shinguards until you can afford more expensive ones. They're much less expensive.
That being said, I bought 20$ (US) shinguards from Title MMA a few years ago and used them for Muay Thai, Pradal Serey, Sanshou and Kyokushin 2-3 per week for 2-3 years and they were perfectly fine. So you should be able to find something reasonable that fits your budget.