is included in Office 365 Midsize Business Editio
n which can be subscribed with a monthly fee of $15. It also belongs to Office 2013 Professional Plus
edition, price about $500 to $600 (volume licencing, price for one license).
If you have any other Office version or edition, you need to buy InfoPath separately. Price about $200 to $250 depending on where you want to buy it. The InfoPath Retail
box or download includes both InfoPath Designer
and InfoPath Filler
As far as I know the only option to get an InfoPath trial version is to download the MS Office 2013 Professional Plus 60 Day Trial
version (download link
). As mentioned above, InfoPath is included in this package.