If you can afford G73,definitely go for it,HD 5870M performs significantly better than a GTX 260M/GT 360M,also it has a quad core CPU,so in games that benefit from milticore CPUs and also in multithreaded apps,you'll benefit from the extra cores.
I haven't heard anything about paying $100 to optimize a system,MAYBE they man that they get $100 and install the windows,drivers etc.
And as for G72,well i7 720QM performs better than a P8700 and its really not worth it to buy a laptop which isn't produced anymore(Core2CPUs are out of production),and like i said 5870M performs better than GTX 260M too.