I just wanted to point out that it can be done. Shoes, necessary, $60-80. Bows, necessary, but you can have a mom make practice bows and your comp bows can easily be less than $20. Schools can have a school set of warm ups - you'll have to fundraise initially but then you're set. Practice wear - unnecessary. White t-shirt, black shorts, every kid has something that will work already, bam, done. So you're looking at right around $100. That leaves $200 for transportation and things like choreo/music/whatever else is deemed "necessary."
You're right - $300 wouldn't go far in an all star world. For high school, though, if you have a different mindset, one that recognizes that student athletes should be able to participate even if their families are not very wealthy, $300 is more than enough. The bells and whistles that we often associate with cheer are not really necessary for the success of the athlete.
OP - it is crazy that your kids can't get a bus, even if the parents are willing to pay for it. That's just nonsense.