The main thing to remember on 1.5 is to play on H campaign difficulty and not VH, just look at the difference in your 2 cmapaigns Dayve, the first one on VH where no one would accept anything, and the 2nd on hard where the ai did accept your offers. THe ai on VH is set up so it wont accept your offers so you have a hard time in the campaign, i find hard is the best difficulty as it allows you to still make offers the ai will accept whist also giving the ai the cheating cash bonus to make things hard.
And unit recruitment costs are perhaps the biggerst factor in deciding what units the ai will spend its money on.