Fans seem to obsess over contracts when some of the big money these players want will never be seen. For example, Tyron Smith was given an 8-year, $97.6 million contract average big money ($12.2 million per year). His cap hit for the first year was $4.976 million, second year was just over $5 million, third was $6.8 million ... would anyone be mad at Thomas receiving that kind of money his first three years? Now, Smith did make $8.8 million the next year and is scheduled to make $17.5 this year (with a base that could be restructured if Dallas wanted).
Eventually, Dallas would have to take a hit if it acquired Thomas and gave him a new deal, but the team could easily get three or four "bargain" years out of him before having to make that decision (which most likely would be absorbed by another player's restructure).
Again, looking at Smith's deal, the final four years pay him $47 million, while cutting him in 2019 would cost Dallas $10.8 million (which would be an almost $4 million cap savings).