Have you looked around the league lately? Guys who can score an efficient 15/6 a game and play decent defense are going to make at least $10-12 million a year. Hell, look at Bosh. He's basically been a 16/7 guy the last two years and he's about to make $40 million over the next two years unless he opts out. That's just what you pay for for that kind of production on a winning basketball team. I'd rather pay $12-14 million a year on Lowry to give me 15/6 than spend $6-7 million a year on a couple of guys who will give me 10/4 in limited minutes.
I do agree that Beverley played well last year and deserves a chance to start again, but I also think Houston just needs more talent on the roster overall. Since they've already got top 5-10 players at their respective positions in Harden, Parsons and Dwight, PG and PF are really the two places left they could make a substantial improvement. If they've got the money and they can't get Lebron/Melo/Bosh/Love to sign, why not go after Lowry instead?