According to reports the Lakers pay Thomas 9 million dollars a year because of luxury tax...
There is something to be said for stepping up to the plate. I am not saying offer him a lot of money, nor insult him. Use your judgment, assess your willingness to pay (an economics term) and make him an offer that you think is fair with regards to his worth and what other teams would offer. If the Spurs are willing to match a full MLE type deal (if somehow KT gets that), it is around ~6 million. So that is the Spurs willingness to pay. Offer him 3.5, which is above what would be considered to low, and way below what you would be ok in paying him. If he accepts than that is great, you essentially saved yourself 2.5 million and took out all the risks of losing him. If he declines, no big deal, because there is a chance (taking all the real world scenarios into consideration such as the Lakers luxury tax problems and the Heat trying to clear cap space) that the 3.5 is the best deal he gets. If he gets an offer for more than that then you know you are willing to go up to 6M to keep him.
Spurs: Kurt, we would like to offer you a 3.5 million dollar contract. We really like what you bring to our team and we want to make you a Spur and get this deal done.
Kurt: hmmm, 3.5, not sure, thank you for the offer, I need some time to see how FA works out, but I will be in touch
Spurs: we know you want to weigh your options, but our deal is on the table and we are going to do what is in our powers to keep you a Spur.
Next day: Lakers offer Kurt Thomas a 3 million dollar a year contract. The Heat have also tendered an offer for an estimated 4 million a year.
Kurt: Well here are my offers, 4 million is what I would like to be paid and if you can up your initial offer to 4 million, I am a Spur.
Spurs: Done, we are glad to have you again and we look forward to this season with you.
Kurt: I want to thank you for stepping up to the plate, giving me time to make my decision and showing loyalty towards me and my family. Lets go to work...