why does price change after buyit now selection? - why not in AUD when commit to buy?

[tony*pitman]

I have recently purchased a number of small items on ebay after conducting detailed comparisons with local stores in my vicinity and other sellers on ebay based on combined shipping and item cost. my initial comparisons saw the ebay total $61.07 and the nearest local store $106.90. i took the plunge and started buying all items on ebay. but i started noticing that after i selected buy it now, the price would change considerably please explain why? also when asked to commit to buy i am not shown the final price in AUD which seems like a leap of faith to me when i cannot see the actual amount that i am paying and commit to buy is non negotiable once selected, why is the total committed price not displayed in the local currency?. by the time i have reached paypal i see that the price has increased yet again can you please explain this? is this an fee applied associated with the use of Paypal to purchase? obviously you are not paypal so i am not looking for a finite answer to this question however some indication of what may be occuring here would be appreciated. in summary the items i purchased amounted to $102.34 just shy of the local store price and at that i would have made a concious decision to purchase locally in the first place and support a local buisness. this is a $41.27 difference from the cost I originally expected to pay on Ebay and I  cannot but think that i have been misled from the outset on the real cost of these items- please provide explantaion on how this will be dealt with.