Are you sure that the storage method for the price is not numeric and is stored as 'R40,000' in the database?
In this case, I believe the best solution is not an input validation on the front-end, that could take ages to get right – to check the first character, then check for thousand separators etc..
Rather, I would recommend validating the data right before it's sent to the database, like so:
This filter will transfer any input to a numeric value, then format it to 'RNN,NNN' format with the thousand separator. I haven't been able to test this with all cases, but it should work. Don't forger to change the $meta_key variable to the meta key that is used for the price filtering.
Please also be careful when making changes to your server files! Always have a back-up just in case.
If you need help with this, let me know. I've also looked up the range slider documentation, and there might be a possible solution to change the slider values based on another field selection, like the built in search has. For that I will have to see a somewhat completed search instance to be able to suggest, as the customization depends on the structure of the HTML output. Let me know if you are interested, I will look into it for you.
The results page layout and individual items content is not affected by the plugin, as it can't be. There is no exact support for that yet in wordpress unfortunately. Some filters may work, but that again depends on your theme as well.Best,
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