It seems to depend on what figures are given.
BoxOfficeMojo gives X3's production budget as $210million, but The Numbers gives it as $150million and then lists one set of marketing costs as $34million. I heard on good authority that marketing was $60m for X3, which if added to the $150million, would indeed make $210million.
The Numbers states this for SR: In Newsweek's July 3-10, 2006 issue, Singer says, "The approved budget was $184.5 million. We had projected overages for visual effects, and there was a sequence that I wanted that was going to cost an extra $2.3 million. So the hard, honest number is $204 million." We (The Numbers) are taking this as the official final budget. Factoring in the tax break (12%) puts the cost at $232 million, and adding the $40 million in previous costs to the studio means that the total expense on the project was in the neighborhood of $270 million.
http://www.the-numbers.com/movies/2006/SPRMN.php
SR shouldn't have cost that much and didn't look like it cost that much (disregarding the previous attempts at a movie and even disregarding the tax break). The production cost of SR is preposterous compared with X3, which had a huge cast of big-name, big-salary actors (Jackman, Berry, McKellen, Stuart) and a lot more action and FX. I think more could have been spent on X3 but, still, it has value for money!