World keep changing at the speed of light. In particular for the technology product, they are usually go to higher version by provide more functionality, more modern application offering, and more bug fixed on the latest version, not to mention for ongoing perfection of the technology offering to the market. As you can see, no product can afford to be static and without change (else it consider obsolete and outdated, the value for such technology is consider questionable). As the enterprise customer now days, all demanding for renewal paid for something, expect to entitlement for the latest software version upgrade and update subscription during the new renewal terms, whether one year to five years (depend on product, some can do up to three years, some can do up to five years).
While above is just one aspect for the answer, technology product keep changing (where manufacturer put in more research and development to provide better product for the market), it had other aspect as well that will provide the answer as part of the variable parameter.
While manufacturer change the product price from time to time, old edition to new edition offering. Exchange rate also had the impact for the contribution for the higher price, since the same value for the respective currency do not equal to the current and future same amount of exchange, either due to international economy climate change, local or inter country politics or fiscal policy changes, or implementing of various value added tax (VAT) or whatever, all also had the same impact on the price change and can not be constant.
Inflation, an economy explanation is a sustained increase in the general price level of goods and services in an economy over a period of time (or deflation) also have the impact on the change. In general, year-to-year rise is what expect from most of stable economy (eg, salary increment year by year), unless the economy is facing dramatic changes that cause deflation.
So the above explain the variable parameter impact on the renewal and explain why the rate can not be the same.
The only exception on this is on foresee future price rise and the need is continue there, E-SPIN arrange for the multiple years contract, and where customer can pay upfront in exchange for the cost saving for the long period of time.
For example, customer A being customer of E-SPIN for couple of years. Customer A is using one of the product, and perceive the value of the product and note on the product in the upward trend. E-SPIN depend on product, some we can arrange for up to 5 years contract value and customer pay in advance for the whole period (for example 5 years), in this scenario and context, no matters what changes for the product price for next 5 years, it will not impact on customer A, since they already contain cost, which indirectly become the procurement saving.