How about this charge controller?
https://www.amazon.com/gp/aw/d/B089SH3W85/ref=sspa_mw_detail_6?ie=UTF8&psc=1&pd_rd_i=B089SH3W85p13NParams#aw-udpv3-customer-reviews_feature_div
$49.90 with free shipping
60a PWM
12/24/36v battery system
States up to 720w if using a 12v system.
Maximum input voltage from the panel: 92v according to the seller.
If these specs are true, then it seems like you could buy two 250w panels for $50x2= $100 and this charge controller ($50) and all the misc other items (~$60) and have a 500w solar system for ~$210.
Note: This requires picking up the panels as shipping makes them too pricy. (I happen to be visiting near where their business is located in Arizona right now.... :-)
What am I missing here? Thoughts?
Chris