Getting alerts on 5 aircraft for free is nice, wouldn’t mind paying a little more to be able to get alerts on 20 or 25. I think the least expensive subscription is aviation+ which is $200/year. How about a $5/month subscription just for getting alerts, please?
It’d cost you less than that in electricity/month to set up a small feeder into the network using a very cheap Raspberry Pi Zero and a crappy RTL SDR dongle from eBay. That would give you the Enterprise subscription.