A spray in pickup bed lining is a great choice especially for a late model truck. However, there are other options. Especially for an old truck, the professional spray on liner may just be too expensive. In that case, maybe you should think about a do it yourself liner.
That is as simple as applying truck bed paint to a properly prepared bed surface. It's not very hard and you can save a bunch of money. There are other really good options for cheaper bed liners too.
Those include simple, cheap rubber bed mats or truck bed carpet. Then there's one of my favorites: the Dual Liner plastic truck bed liner. This is a multi-piece rubber and plastic liner that's very tough, but looks good too. Much cheaper than a spray on liner too.