No, it is not scam. It is YOUR choice if you want to buy them. If you don't want to buy them you can still buy the items for the full prize during sales. Scam would be if you have no chance to get the listed item. It is just luck in this case.
It's exactly what it is, no rng percentage and no ensurance of getting item after a certain number of tries lol Anyway, How much could it cost for the "full price" you mentioned before, and when could I be able to purchase it? (premade date or ?)
The M39 EMR Black Mamba is an "Epic" collection skin which only can obtained by getting all 3 weapons. The Pixel MSBS can actually not be directly obtained by Chips. You have to either get it from the "Collection Box" or in a sale in the webmall.
The webmall changes frequently so checking it from time to time makes sense. If you don't want to spend money, you have to use the previously mentioned "Collection Boxes" (50 Chips each). But be warned, the drop rate is quite low and getting the Pixel MSBS is very rare...