The prices are truncated, so you can't see the actual costs, which are increasing every purchase. But, eg, the last one can cost almost 2K and still _say_ 1K as the price (but trying to buy it won't work)
This is on purpose, if I showed the full prices inside of those buttons I would not have nearly enough space, so I had to truncate and round the prices.
I had experimented with all sorts of different placements for the price and I decided to round and truncate them. Through my testing, I found it as the best placement and rounding for the price.