It's a tradeoff of gold vs. speed and farming time. Going strictly by the gold cost, it is always cheaper to level with monos than with basics... but basics give you points much faster, and you'll accumulate large stacks of them while farming anything else.
For armor without water or earth the cost for using snakeskins and monos becomes equal when enhance cost reaches 2000 per slot; after that, snakeskins are cheaper (but slower and take more farming time). For earth or water armor, the costs are just about equal when enhance costs 1300 per slot.
If fusion stones are considered free, then for non-matching armor it becomes cheaper to combine two basics into a 50-point and enhance with that when enhance costs over 12,000 per slot, and for earth/water 18,000 per slot. This is of course much faster than using snakeskin.