Makro and costco aren't that easy to price up - and I think most cash and carrys work in the same way.
The price is on the shelf (plus VAT where applicable) but that is not the price the majority of customers pay. The more you spend the bigger discount you get at the till - so if you just buy one box of washing up liquid every six months, yes you do pay the shelf price which is often as dear as your local supermarket.
If you have a large turnover though and spend a lot of money in store, you get a discount. The higher the spend, the bigger the discount.
Wholesalers don't like giving their prices out - they don't want you to know how much profit your corner shop is making. :)
It's going to be difficult - can you do your pricings based on local supermarket prices minus 15% - 20%? That is probably the sort of discount you will get until your turnover increases/