only you can decide if it is 'worth it' but before making that commitment you should 'shop around' for a shop/dealer that has a set up you could try out- or a friend, quilt shop, *try it before you buy it* when you quilt on your domestic machine without a frame you can manipulate your quilt around to get to all the areas- this 'process' is limited when using a frame- and the frame does take up 'throat' space- so by the end you may only have 2"- 4" of quilting space to work in- depending on how large the quilt is- so, you would really want to plan your design. some people love using the frames- some find it very *restricting* ~~ but as with most things each of us are different- and only you can decide what is best for you.
as for the 'affordable, quality long arm machines' affordable is a relative term & means something different to each of us- I may have believed the $10,000 I spent on my long arm was a great deal- where you may find that to be not affordable at all...
again, call around, visit dealers, shows, shops, check them out- ask questions, test drive (they are an investment and you need to find the one YOU like-just like buying a car) then, when you find what you like/want you could start looking for used ones in a price you are comfortable with- but don't make the investment (blindly) without having at least tried them out- because the 'thought of owning one' is appealing.