hi Egil,
I can offer some advice on this if you like, im guessing the cost of the last pack you bought was 19.99$ which makes you next pack offers i believe 49.99$ once that happens it takes a while for the cost to drop again to 19.99$ then to 9.99$, its done by some sort of algorithm which plarium dont influence so not much they will do about it,the best way to buy packs that i have found is to buy the reduced ones say 199.99$ reduced to 19.99$ or the lower priced ones but always end with buying a pack for 4.99$ reduced from higher price then your packs will stay at 4.99$ apart from the type of pack you purchased say a resource pack, this doesnt work if the 4.99$ isnt one thats reduced from a higher price,
and to answer your question if you should stop buying packs the answer is yes dont buy anymore packs until the price drops or it will just stay as it is
try to wait around 8 weeks or so that way you might even start to see mega packs appear,
hope this is of some help.
Andy