Make certain part of text bold using DataBinding

You have to create a BindingAdapter and SpannableStringBuilder .

Binding Adapter

object Util {
    @BindingAdapter("main","secondText")
        @JvmStatic
        fun setBoldString(view: AppCompatTextView, maintext: String,sequence: String) {
            view.text = Util.getBoldText(maintext, sequence)
        }



    @JvmStatic
        fun getBoldText(text: String, name: String): SpannableStringBuilder {
            val str = SpannableStringBuilder(text)
            val textPosition = text.indexOf(name)
            str.setSpan(android.text.style.StyleSpan(Typeface.BOLD),
                    textPosition, textPosition + name.length, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
            return str
        }
}

XML

    <android.support.v7.widget.AppCompatTextView
        android:id="@+id/username"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:main="@{`you will pay $160 for your pair`}"
        app:secondText="@{`$160`}"
        android:textColor="@color/black"
        android:textSize="22sp" />

May be it helps you.

As per @CommonsWare,

Tried by adding basic Html tag <string name="product_price">If you are selected, you will have to pay <![CDATA[<b>$%d</b>]]> for your pair.</string>

Layout File : Imported Html

 <?xml version="1.0" encoding="utf-8"?>
 <layout
   <data>
   <import type="android.text.Html"/>
   <data>
     <LinearLayout>
       <android.support.design.widget.CoordinatorLayout>
       <TextView
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_marginEnd="@dimen/spacing_xlarge"
          android:layout_marginStart="@dimen/spacing_xlarge"
          android:layout_marginBottom="@dimen/spacing_small"
          android:text="@{Html.fromHtml(@string/product_price(productPrice))}"
          android:textColor="@color/button_tertiary"
          android:visibility="@{productPrice > 0}"
          style="@style/Body.Small"
          />
       </android.support.design.widget.CoordinatorLayout>
     </LinearLayout>
 </layout>