Solved. After the edit it was easy. It is allowed to use type => ‘decimal(x,x)’ in meta_query. Maximum precision is decimal(65,30).
https://dev.mysql.com/doc/refman/5.7/en/precision-math-decimal-characteristics.html
array(6) {
["orderby"]=>
array(2) {
["uss_product_price"]=>
string(4) "DESC"
["title"]=>
string(3) "ASC"
}
["meta_query"]=>
array(3) {
["relation"]=>
string(3) "AND"
["sortprimary_clause"]=>
array(3) {
["key"]=>
string(17) "price"
["compare"]=>
string(6) "EXISTS"
["type"]=>
string(13) "decimal(30,5)"
}
[0]=>
array(4) {
["key"]=>
string(17) "price"
["value"]=>
array(2) {
[0]=>
float(0)
[1]=>
float(9999)
}
["compare"]=>
string(7) "BETWEEN"
["type"]=>
string(7) "decimal(30,5)"
}
}
["tax_query"]=>
array(1) {
["relation"]=>
string(3) "AND"
}
["post_type"]=>
string(7) "product"
["posts_per_page"]=>
int(15)
["paged"]=>
string(1) "2"
}