There are many subjects in this General discussion part that trigger and old layman's curiosity, so also this discussion. I found a site said to rank the ten best Elasticsearch hosts. When reading on the Elastic search homepage and in this thread that a minimum of 8 Gb ram is needed. But these hosts offer plans from 0.5 Gb ram and 5 Gb storage. Another 1 Gb ram and 20 Gb storage. 8 Gb ram is about 160 € per month.
So how to calculate what you need. Some of the hosts say that RAM should range from a 1:20 dataset size for low search volume to 1:1 for high search volume. I assume that a shop can be in the low range.
Now the layman shows. What is a dataset in this context?