Hey man! So yeah, I am probably the wrong person to ask, since I am just screwing around with Steem Monsters. But here is what I know.

First, keep in mind, $3 USD is still like 9 STEEM at current market rates. So if you are looking to build STEEM, then that's still not a terrible return. I've gotten lucky and hit the Lord A guy several times. I know as you upgrade him he gets abilities that can make him a pain in battle, but I also know I have defeated nearly every deck I have seen him in, so I am not collecting that particular card.

The level caps are based on your current league ranking and your summoner level. So when I was playing in Silver League, my Level 6 cards might be knocked down to level 3 in order to make it fair versus other silver league members, but as I climbed the ladder, my levels caps went up so my cards powers increased.

For me it is all about return on time invested. If a card is currently selling for 2-3 cents on the market, then I am not going to go to the hassle of listing mine, especially if I have say 10 of that card available. Just not enough return on time invested to set those cards for sale.

Flipping the coin, I don't see the value in having a card sitting at Level 6 13 of 47 cards toward level 7 or whatever the algo is. So I will upgrade a card to the next level, and if there is a value proposition in selling the card, then I sell the rest. Inevitably I will collect a lot of Reward Cards for completing daily tasks before I remember to look at leveling up again, so I might have 36 of 47 and decide not to sell that card and hold it to upgrade to the next level when I get enough of them.

I dunno man. That's how I play it. But pose the questions in a post and tag it with SteemMonsters and see what kin of opinions you get back. I have the good fortune to have my investment in cards so far in my rearview mirror that I just assume every STEEM brought in is profit at this point, and I know that is not everyone's perspective.

Hope this helps some!!