master.xml

<?xml version="1.0" encoding="UTF-8"?>
<data>
    <products>
        <entry id="1">
            <name>Test</name>
            <public-price>10.00</public-price>
            <trade-price>8.00</trade-price>
        </entry>
        <entry id="2">
            <name>Test</name>
            <public-price>10.00</public-price>
            <trade-price>8.00</trade-price>
        </entry>
        <entry id="3">
            <name>Test</name>
            <public-price>10.00</public-price>
            <trade-price>8.00</trade-price>
        </entry>
        <entry id="4">
            <name>Test</name>
            <public-price>10.00</public-price>
            <trade-price>8.00</trade-price>
        </entry>
        <entry id="5">
            <name>Test</name>
            <public-price>10.00</public-price>
            <trade-price>8.00</trade-price>
        </entry>
    </products>

    <prices>
        <entry id="6">
            <product>
                <item id="1">Test</item>
            </product>
            <public-price>15.00</public-price>
            <trade-price>14.00</trade-price>
        </entry>
        <entry id="7">
            <product>
                <item id="2">Test</item>
            </product>
            <public-price>12.00</public-price>
            <trade-price>11.00</trade-price>
        </entry>
        <entry id="8">
            <product>
                <item id="3">Test</item>
            </product>
            <public-price>18.00</public-price>
            <trade-price>15.00</trade-price>
        </entry>
    </prices>

    <offers>
        <entry id="9">
            <product>
                <item id="1">Test</item>
            </product>
            <public-offer-price>5.00</public-offer-price>
            <trade-offer-price>4.00</trade-offer-price>
        </entry>
        <entry id="10">
            <product>
                <item id="3">Test</item>
            </product>
            <public-offer-price>6.00</public-offer-price>
            <trade-offer-price>5.00</trade-offer-price>
        </entry>
        <entry id="11">
            <product>
                <item id="4">Test</item>
            </product>
            <public-offer-price>7.00</public-offer-price>
            <trade-offer-price>6.00</trade-offer-price>
        </entry>
    </offers>
</data>

master.xsl

<?xml version="1.0" encoding="UTF-8"?>
	<xsl:stylesheet version="1.0"
					xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
					xmlns:exsl="http://exslt.org/common">
					
		<xsl:template match="/">
			<xsl:variable name="offer-merged-products">
				<xsl:apply-templates select="data/products/entry" mode="merge-prices" />
			</xsl:variable>	
			<table>
				<thead>
					<tr>
						<th>Product</th>
						<th>Price</th>
					</tr>
				</thead>
				<tbody>
					<xsl:choose>
						<xsl:when test="$user-type = 'trade'">
							<xsl:apply-templates select="exsl:node-set($offer-merged-products)/product" mode="display">
								<xsl:sort select="exsl:node-set($offer-combined-products)/trade-price" data-type="number" order="descending" />
							</xsl:apply-templates>
						</xsl:when>
						<xsl:when test="$user-type = 'public'">
							<xsl:apply-templates select="exsl:node-set($offer-merged-products)/product" mode="display">
								<xsl:sort select="exsl:node-set($offer-merged-products)/public-price" data-type="number" order="descending" />
							</xsl:apply-templates>
						</xsl:when>
						<xsl:otherwise>
							<tr class="error"><td colspan="2">Unknown user type!</td></tr>
						</xsl:otherwise>
					</xsl:choose>
				</tbody>
                	</table>
		</xsl:template>

		<xsl:template match="data/products/entry" mode="merge-prices">
			<xsl:variable name="$current-product-id" select="@id" />
			<xsl:variable name="$offers-node" select="/data/offers" />
			<product>
                        	<name><xsl:value-of select="name"/></name>
				<xsl:choose>
					<xsl:when test="$offers-node/entry[product/item/@id=$current-product-id]">
						<public-price>
                                  			<xsl:value-of select="$offers-node/entry[product/item/@id=$current-product-id]/public-offer-price" />
						</public-price>
						<trade-price>
							<xsl:value-of select="$offers-node/entry[product/item/@id=$current-product-id]/trade-offer-price" />
						</trade-price>
					</xsl:when>
					<xsl:otherwise>
						<public-price><xsl:value-of select="public-price" /></public-price>
						<trade-price><xsl:value-of select="trade-price" /></trade-price>
					</xsl:otherwise>
				</xsl:choose>
			</product>
		</xsl:template>

		<xsl:template match="product" mode="display">
			<tr>
				<td><xsl:value-of select="name"/></td>
				<td>
					<xsl:choose>
						<xsl:when test="$user-type = 'trade'">
							<xsl:value-of select="trade-price"/>
						</xsl:when>
						<xsl:when test="$user-type = 'public'">
							<xsl:value-of select="public-price"/>
						</xsl:when>
						<xsl:otherwise />
					</xsl:choose>
				</td>			
			</tr>
		</xsl:template>
	</xsl:stylesheet>