From how I understand the comp system in general, the amount you spend or lose is irrelevant. As mentioned, slots are easy to rate with coin in.
From my understanding, we are rated at tables on our average bet. Each game has its own theoretical loss % and number of hands or games per hour and that number is extrapolated over our time played and we are turned into a number based on that.
If you sit down with $1000, play $200 a hand over 20 minutes and lose it all and don't return, you have very little value to a casino.
A $25 a hand player that spends 24 hours playing over a week and ultimately loses $1000 is a more valuable player than the $200 bettor.