Only thing about some of them bonuses is they have crazy rules to actually ever be able to cash out the bonuses. I was using Bovada that doubled the initial deposit. The kicker was you had to bet 17x the bonus amount within three weeks to ever be able to cash out and if you didn't they drained the account. I had to cuss some people out on customer service to get it extended just one week and I just placed a bunch of long term bets with the rest of the money. Soon as a couple of them hit I withdrew immediately and ain't fukked with them since.
Bovada and pretty much any overseas sportsbook with have a minimum of 10x roll over. That's why I don't take the deposit bonus on those books because unless you're on absolute fire and get pretty lucky, you're not rolling through that amount. If I deposit $1,000 and they match $500 or something, I have to WAGER $17,000 if there's a 17x roll over. If you use the casino there, the roll overs are often even higher outside of slots.
I have not seen a high rollover amount on any legalized books in the U.S. though. I think maybe the highest I saw was 2x? However, they usually seem to be a 1x roll over of what you deposited for the most part. The ones where you get your first bet back if you miss are the best ones if you have the cash to deposit a lot.