I think that if you don't want to spend the money on a beauty blender($20) that you will be fine going with an alternative. However, I think that the beauty blender is the best foundation sponge on the market. I personally use and love it. I avoided buying one and tried sponges from different brands. Eventually, I just bit the bullet and purchased it. I do not regret it at all. It gives me great coverage (with the foundation I use) and doesn't soak up the product.
Popular Alternatives:
Tarte Sponge $16- Way too dense and it's too hard to bounce on you face to blend out foundation and concealer.
Real Techniques Sponge $6.99- Soaks up too much foundation so you loose product and sheers out the product so you don't get proper coverage.
Morphe Premium Sponge $6.99- This is the most comparable of the three to the original beauty blender. Blends out product quickly and effectively. The only negative is the inconvenient shape that can make it difficult to blend out under eye concealer.