Adobe Experience Manager is an enterprise level collection of server apps - you need a Windows or Linux server to run it. The cost of the server is very small compared to the cost of AEM. The price is "on application" and by negotiation but expect it to be 5-6 figures (US dollars). Often board level approval is needed, but it is aimed at the whole enterprise, not just making a form. (If your question is about AEM Designer, rather than AEM Forms, then there is a cheaper answer; however the forms it makes are OBSOLETE if you do not use the full AEM forms server app).