Complex sentence: When it was introduced, the 6502 was by a considerable margin, the least expensive full-featured microprocessor on the market, selling for less than one-sixth the cost of competing designs from larger companies, such as Motorola and Intel.
Split into simpler sentences: When it was introduced, it was the least expensive, by a considerable margin, full-featured microprocessor on the market. The 6502 cost less than one-sixth the price of competing designs from larger companies such as Motorola and Intel.