For a Republica Mexicana 50 Centavos, 88,000 turns out to be a fairly typical mintage figure. The output of 50 Centavos at the other branch mints that year were: Chihuahua - 26,272, Culiacan - 75,802, Durango - 28,133, Guanajuato - 18,000, Potosi - 32,400, and Zacatecas - 63,000.
As you know, the value of any coin is driven by supply and demand. For the 1887 MO M 50 Centavos, valuation is made difficult by the combination of low demand and very low supply. There appear to be only a few people interested in collecting this series. This is counterbalanced by the fact that are very few problem-free AU or Uncirculated examples remaining.
The end result of this "thin market" is that a high-quality coin might auction for a much higher price than you would expect, while a similar coin in Fine condition can sit in a dealer's inventory for years.
Is your coin XF or better?