C3 nets are pricey indeed, but can be veeerrrryyy worthwhile. For me it often comes down to the composition of the enemy and whether I'm attacking or defending. Of course you don't necessarily know those things before the game so it can be a bit of a crap shoot.
Considering how big a deal fast units are, especially ones diving into woods, improving your to-hits with C3 becomes a huge advantage. If I were fighting in a wooded area, or on offense against a prepared enemy, I'd rather have a full C3i net instead of, say, eight mechs but no network. Even if you have artillery for hitting the fast movers, C3 can still help you wolfpack an assault mech and knock it out in one turn.
The main things is that C3 nets are very front-loaded. While the network is intact it is very powerful. But when you start losing units (or you don't have any ECCM) shit starts to go downhill fast. That's when you start feeling the PV hit most.
So yes, C3 is limiting in terms of your PV. But 500 is plenty of points, especially if you incorporate some cheaper tanks (I think even BA) in place of some mechs. Just make sure you anchor a formation with at least one heavy hitter. If you can't set up an assault mech with a 3 or 4 point long (or 5 point medium) range shot every turn you're doing it wrong.