We are wondering how hard it would be and expensive to clean up all the used cups, holders ect and re pour new high grade scented candles back in to sell as new reconditioned?

Difficulty is rather subjective.

How difficult to clean up the holders? IMO, not very. Time consuming, yes, difficult no. Much of the wax can be removed by heating the container up just enough to melt the wax so it can be poured out. Then while the wax residue in the jar is still molten wipe the jar out with a rag. Obviously proper safety precautions like ovenmitts or tongs need to be employed. If you do an online search, you will find a number of good sites that go over how to safely heat wax such as use of a double boiler.

Additional wax residue can usually be removed after the container has cooled by using a solvent such as Goo-Gone.

As far as expense, that too varies. The wax from the old candles can be recycled. I find an array of small butter tubs (or similar) to work well for this. As waxes are melted the colors can then poured into the various containers to be kept separate. Once the wax has cooled completely (a freezer or the great outdoors if you live in a temperate zone that is currently experiencing temps in the 50's or below works great -- colder the better), the wax can usually be "popped" out of the container not unlike icecubes out of an icecube tray. The wax can then be bagged up by color to be pulled out for melting as needed.

Many of the wicks may even be reuseable to some extent. If a wick has been partially burned, snip off the burned portion and use the wick in a shorter candle container.

Clean cans from soup or canned fruit and such, can be used as melting pots for the waxes. Old pots can be used for the water bath of the double boiler. I use a cheap second hand electric skillet/pan to server as my water bath portion.

Cheap second hand cooling racks will be needed for freshly poured candles to cool upon.

So far, quite cheap, yes?

Now the more expensive stuff:
additional wax if needed
wicks and tabs
fragrances if desired
dyes

Note: Wax from pillar candles does not make good wax for poured scented candles. Scented candles require a wax with a low melting point so a large melt pool can form as this is how the scent is released. You can, however, blend the pillar wax with soy wax in 50/50 ratio or better a 25/75 ratio and get satisfactory results.

Wicks and wick tabs are usually very cheap (like 100 tabs for about $2, can't remember wick prices but they tend to be very cheap too).

Fragrances will be the most expensive items if you choose to use those. Do not go to craft stores such as Michael's for scents. IME, they tend to be far more expensive and often of lower quality than those offered at dedicated candle supply store. If you have a store near you, go and check out their offerings. If not, there are some decent online stores. Prices are often about $2.50/oz and you will generally need 1-1.5oz of fragrance oil per pound of wax to get a decent scented candle.

Dyes can be purchased as concentrated solid wax blocks/pieces or as liquids. DO NOT try to use food coloring! Food coloring is a water based dye and water and wax do not mix. Dyes will be cheaper than the fragrances as they go a lot farther. Again, as with fragrances, the dyes from a candle supply store will gnerally be far cheaper and better quality than that at a hobby store.

There are a number of waxes available. Soy is one of the most popular. No matter what wax you decide to go with (assuming you need to buy more), candle supply stores will be a better deal than a hobby store. At a supply store I recently visited, I got 5 lbs of soy wax for about $9.

Make sure you have a digital scale for weighing out the wax and fragrances -- guess work is So hit or miss (and usually miss).

Since Paul already answered this so very well, I will just add a few places you may want to check out for supplies. Bolekscrafts.com and rusticescentuals.com are two very good places for your supplies and very reasonable. Rustic has reviews of all the scents, where boleks does not, but boleks has some great pricing on the majority of their products. Both are very good though, so much luck!