Table:
|  | Year ended December 31, |  |  |  | Year ended December 31, |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| (in thousands, except percentages) | 2019 | 2018 | $ Change | % Change | 2018 | 2017 | $ Change | % Change |
| Cost of revenues |  |  |  |  |  |  |  |  |
| Subscriptions | $160,320 | $109,454 | $50,866 | 46% | $109,454 | $89,193 | $20,261 | 23% |
| Other | 70,723 | 47,675 | 23,048 | 48% | 47,675 | 32,078 | 15,597 | 49% |
| Total cost of revenues | $231,043 | $157,129 | $73,914 | 47% | $157,129 | $121,271 | $35,858 | 30% |
| Percentage of revenues |  |  |  |  |  |  |  |  |
| Subscriptions | 18% | 16% |  |  | 16% | 18% |  |  |
| Other | 8% | 7% |  |  | 7% | 6% |  |  |
| Gross margins |  |  |  |  |  |  |  |  |
| Subscriptions | 80% | 82% |  |  | 82% | 81% |  |  |
| Other | 17% | 22% |  |  | 22% | 16% |  |  |
| Total gross margin % | 74% | 77% |  |  | 77% | 76% |  |  |
Paragraphs:
Cost of Revenues and Gross Margin
Subscription cost of revenues and gross margin. Cost of subscriptions revenues increased by $50.9 million, or 46%, during fiscal year 2019 as compared to fiscal year 2018. Primary drivers of the increase were increases in third-party costs to support our solution offerings of $21.5 million, infrastructure support costs of $19.8 million including amortization expense from acquired intangible assets, and headcount and personnel and contractor related costs of $9.6 million including share-based compensation expense. These factors resulted in a decrease in gross margin.
The increase in headcount and other expense categories described herein was driven primarily by investments in our infrastructure and capacity to improve the availability of our subscription offerings, while also supporting the growth in new customers and increased usage of our subscriptions by our existing customer base. We expect subscription gross margin to be within a relatively similar range in the future.
Other cost of revenues and gross margin. Cost of other revenues increased by $23.0 million, or 48%, during fiscal year 2019 as compared to fiscal year 2018. This was primarily due to the increase in services personnel costs of $11.1 million including share-based compensation expense, cost of product sales of $10.6 million, and overhead costs of $1.3 million. Other revenues gross margin fluctuates based on timing of completion of professional services projects and discounting on phones.
Question:
What is the average cost of subscription between 2017 to 2019?
Answer: (89193 + 109454 + 160320)/3  = 119655.67