Holdingcalves is a risk, but can be worth it if you manage them. Calves hit a low in the summer and I am hopeful they will rise into winter/spring. In my area the 500 lb calves are bringing the same per pound as the 400lb calves. With this being said, it comes down to your price per pound of gain to get that extra 100 lbs on them. That's for you to figre out. People always told me "weight is your friend" when it comes to selling calves.
Steers in my area are going for around 1.85 for a 400 lb steer so that would end up being $740. Then the 500 lb steers area around 1.78 so that would end up at $890. Now in our area feed is around $275 to $300 per ton give or take and it ends up costing about $0.85 per pound of gain. So to put on 100# it would cost around $85 depending on current feed costs ending up at a $65 gain per head. It usually takes around a month to gain 100# depending on your genetics and feedstuffs so $65 dollars over 30 days is over $2 per day per head. Now in my case in background feeder cattle that would sound really good to me if you end up with those prices and gains, in the end its up to you but i like to feed out our home grown cattle, it usually ends up being worth it depending on the market.