Echoing the sentiments of agent Happy Walters a night earlier, Marcus Smart said Tuesday morning that if the Celtics want to keep him, the cost will be higher next summer in restricted free agency than if they had met his rookie extension wishes this week. “That’s exactly how I’m looking at it. I think that’s how every guy looks at it when they go into free agency,” the Celtics guard said during Tuesday’s shootaround at Quicken Loans Arena. “You make a lot more than what the team could have got me for now and locked me up. But that’s OK. It’s not a bad thing. Everybody’s making it out like, ‘Oh, that’s a bad thing.’ It’s not a bad thing. Just hoping it’s gonna be a fun year and just play it out.” Smart stressed that he wasn’t looking for the kind of rookie max payday that was showered on Philadelphia’s Joel Embiid and Minnesota’s Andrew Wiggins, and that his hopes were reasonable. But the Celtics’ fears of a high luxury tax in 2018-19 got in the way. “We thought it was close from the fact that we didn’t ask for much,” he said. “We were going to take less money than what we probably are valued, and some other things, but they just weren’t budging.