Which mathematical concept has Texas Instruments famously incorporated into their pricing strategy for their high-end graphing calculators?

In the competitive world of educational mathematics products, pricing strategies often determine market success. One particular mathematical concept has been leveraged by several leading brands to set their price points for premium calculators, textbooks, and educational software. This approach not only appeals to mathematics enthusiasts but also creates a subtle psychological effect that influences perceived value and purchase decisions.

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The Golden Ratio (approximately $159.99, which follows the 1.618... proportion from their mid-tier products)
Fibonacci Sequence (pricing each new model at the sum of the two previous models' prices)
Prime Number Pricing (ensuring all flagship products are priced at prime number values like $101.99 or $127.99)
Pi-based Pricing (using multiples of $31.41 to create memorable price points that mathematics enthusiasts recognize)