To be a bit more precise, themes are showing product prices on results. Not WPSOLR.

Indeed, WPSOLR found that Product1 has at least one variation with a price in the filter range 4000-5000.
But your theme is showing Product1 with a default price (lower variation price perhaps) not in the filter range.

Some themes can show the price range of variations on products results, $2,000-$4,000 for your example.

You could also customize your search results price to show the intersection of filter range and price range (in the url as parameters), $4,000 in your example (intersection of 2000-4000 and 4000-5000)

You want to index all your products with a single variation price, the lowest?

Here is the idea: replacing the product _price just before sending the product to the index.

<?php
use wpsolr\core\classes\WPSOLR_Events;

add_filter( WPSOLR_Events::WPSOLR_FILTER_SOLARIUM_DOCUMENT_BEFORE_UPDATE, 'update_price_with_lowest_variation_price', 99, 5 );

function update_price_with_lowest_variation_price( array $document_for_update, $solr_indexing_options, $post, $attachment_body, $search_engine_client ) {

	switch ( $post->post_type ) {
		case 'product':
			$document_for_update['_price_f'] = /* calculate new  price here from wc_get_product( $post->ID ) and its variations */;
			break;
	}

	return $document_for_update;
}

calculate new price here from wc_get_product( $post->ID ) and its variations

You can do whatever you want to calculate the price here.
You will need to reindex your products to see the price facet updated.