Several months later, now that I have plenty of CPU, polling the market every tick is indeed nothing to be concerned about.
When I wrote this comment I had a very very low GCL with maximum remote mining consuming 100% of available CPU - polling the market looking for deals all the time was not insignificant overhead that was preventing me from leveling up my GCL at maximum speed, which was (and still is) my primary concern.
FWIW I am fairly active in the subscription token market now. Because of the market's poor implementation, it is easy to make a lot of credits by setting buy orders at very low prices. Along comes a low GCL player who is forced to sell to me even though my pricing is not at all competitive, and voila! I've made a small fortune. Rinse and repeat.
Am I happy that it's so easy to make credits if I use the system like this? Not really, but I do it anyway. Does it show that the market is working? No. It only illustrates how broken the market really is when it comes to forcing new players to use buy orders rather than allowing them to create competitively priced sell orders.