First of all - is the size. Depending on a size the price of tubes are formed. The most common Nixie tube IN-14 has a middle size and thus is the most affordable and popular. The second criteria, which is also considered is a shape of "5" digit. The most available and common Nixie tube IN-14 has a upside-down "2". Due to some reasons (probably economy) soviet engineers decided to reuse some materials. For more obvious comparison see the image below.
Shipping is $10 for any number of tubes. Shipped via International Air mail with tracking number.
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